Wiring Notes and Related Information
First posted:  Mar 2018  R. Kwas  Revisions on-going  [Additional Comments]

Some new, some material previously published on the SW-EM site.


Wire Gauge vs Current
The Lowly .250" Push-On Terminal
Wire Strippers
Crimp terminals, Tools, and making a Proper Crimp
Crimping Tools
Making a Proper Crimp
The Lineman's splice
Notes on Making In-Line Connections

Soldering Notes
(Pre)-Tinning Soldered Connections
Digital Solder Stations
Lead Poisoning?...Hogwash!
Lead-Free Solder Sucks! 

Practical Applications of Soldering on a Vintage Volvo
    (Re)soldering Window Lift Cable on a 122
    140 Instrument Panel Repair by Soldering Swaged Pins

Important Reference Information for Soldering


Wire Gauge vs Current

Wire gauges: 

Lighting circuits to 10Amps:  18ga.

Charging circuit to 60A:  10ga.

Reference also:  https://www.engineeringtoolbox.com/amps-wire-gauge-d_730.html 


The Lowly .250" Push-On Terminal is a little marvel of design and function.  It has been engineered to allow a highly reliable, semi-permanent, high current connection to be quickly and effectively made, which still can be disconnected by hand with minimum effort.  It is inexpensive, and simple to be installed onto wires at the factory in a high volume production environment with automated tools, as well as being able to also be installed one at a time with hand-tools (see below!), by Joe-weekend-vintage-Volvo-mechanic....

...the two curved sides of the female contact are effectively a single turn spring (with variations, see below), which keep the two connection areas under constant preload...this accommodates any production dimensional variations, as well as thermal dimensional changes and vibration in-service very well…any variations, are continuously taken up by the constant preload! 

.250" terminal conceptual drawing showing a typical version on the left,
and another version, with even higher contact pressure (because of decreased contact area), on right. 
Spring preloaded electrical contact is made at three places, two at edges on topside, one at retention dimple on bottomside.

...they make a very good mechanical and electrical connection, with the cutting action during connector mating assuring two virginal metal surfaces.  This can be considered a Low-Contact Area/High Force situation.  Add the benefits of long-term protection by ACZP, and we have a semi-permanent electrical connection very well suited for, automotive applications…again, good engineering at work! 

Special versions of 1/4" contacts:  

Fully insulated 1/4" crimp terminals.  Once mated, in an in-line connection,
there are no exposed conductors to make inadvertent contact with anything!

...but beware...there are ways to get it wrong, too...in making harnesses for some of the SwEm Kits, I like the complete coverage of the fully insulated, female crimp-on contacts (...nothin' but the best for my customers!)...shown below is one of these female terminals being pushed on the male terminal of a Brake Light Switch...wrongly!  It is possible to incorrectly insert these onto the mating terminal...this might make a good electrical connection today, but might become intermittent or even work its way apart tomorrow under vibration, because the mechanical connection does not have the retention force of the engaged dimple/pimple.

Insert carefully and correctly when using these terminals!  (Shown clean below for detail, but in service, should have a protective coating of ACZP!)

1/4" female terminal misinsertion...possible because slots on either side of the actual terminal allow this. 
This is an example of poor design!  This should not be possible, as an example of poka-yoke
In kits, this connection is gooped up with ACZP, but that would obscure what we need to see here...


Related Excerpt from a Forum THREAD:  http://www.volvoforums.org.uk/showthread.php?p=2040833#post2040833

"Problem solved, was oil/grease buildup on both electrical contacts. No disassembly required."

My response:  "Be aware...if "oil/grease buildup on both electrical contacts" is enough to prevent electrical contact, the spring preload of push-on terminal (which should be present!) must not have been very good, because by design, pushing on terminals should cut through oxidation and surface contamination to allow contact of clean metal surfaces. This means after cleaning terminals of switch, you may want to (at the very least) squeeze (female) terminals to restore some preload, and (at the very most) replace crimps with new! ...and of course: Apply ACZP!" 


Wire Strippers:  

Many different styles and variation of wire strippers exist.  Below are shown some of the more common styles, presented somewhat in order of cost and effectiveness.  The important thing to note is to use the correct cutting area by gauge, or if adjustable, make a test-stripping or two in order to adjust for the wire gauge being stripped so that only insulation is cut and not the conductor strands...even just nicking the strands is very undesirable as it immediately decreases the conductor cross sectional area (which will increase the I2R losses aka: Make HEAT!  See also:  http://www.sw-em.com/gastight.htm#I2R%20Heating ), and any nicked strands also present a mechanical stress riser where vibration may (will) in the long-term, cause further failure.  In extreme or critical cases such as motorcycle or aircraft duty, or after a long time under vibration, complete breakage will result!  [This is why the author abhors Scotchlok Connectors (and any other connector using Insulation Displacement for that matter!  There are good reasons you would NEVER...EVER find any of them in aircraft!)]

Here is a good example of what should make your blood run cold!

Naturally, the less expensive the stripping tool, the easier it is to get it wrong, but operator care and judgment (and use of ACZP when making and connecting the crimp!) are always called for to get good results over the long-haul...

Very Good Strippers: 

Cutting insulation of various wire gauges, and pulling away the insulation in one operation when squeezing the handles.  Also good for areas with low elbow room!   Modest in price but also with a low chance for nicking a wire...a good combination!  This is the only style stripper I would use when wiring an aircraft!

Squeezing the handle first cuts insulation (only, due to precision jaws), then pulls it away, in one operation.  These were the strippers of choice for a high-volume production environment for a long time, and they are still very good, but they have been surpassed by the one shown on the right as those further remove operator error, and possibility of nicking a conductor!  In the stripper on the left, the operator must insert wire into correct blade gauge location...if inserted into a smaller gauge location than the wire to be stripped, damage to the conductor will still result.    Both styles are for single handed operation, and so good for use in areas with low elbow room! 

Because of the risk of nicking a wire in all strippers following, I would NOT use any of them for wiring an aircraft! 

A high quality (German) stripper.  Jaw closure must be set for a given wire gauge.  Squeezing the handle only cuts the insulation...which must be pulled away in a separate operation so these require a bit more elbow room to use.  Conductor can be nicked if not adjusted correctly!  ...again operator plays a significant part in getting it right!

The following strippers can be levered against a needle-nosed pliers which is holding the wire to be stripped, so they are well suited to confined areas as the action is gentle and controlled. 

Mid/Low Price: 

Adjustable, in that, operator must insert wire into correct blade gauge location.  These have a "Squeeze Stop" to help prevent over-squeezing.

Low Cost (but I'd still rather have them than strip a wire with my pocket knife!): 

Least expensive strippers, requiring setting of the "Squeeze Stop" by operator...of course if one is just stripping one lousy wire, one might be tempted to leave the Stop backed way off so that they can also be used as a cutter, and simply use judgment, and "under-squeeze" to cut ONLY insulation...but beware, if the stop is not set, there is a high risk of nicking the conductor which must be managed, because what is a stripper when under-squeezed, will quickly become a cutter when over-squeezed!!  Use only with Care and Caution!

How long should the stripping (un-insulated wire length) be?  Answer to this is arrived at after an inspection of the terminal to be crimped...  In general, length should allow stripped wire to fully protrude into crimp barrel to be visible at the other end, but not protruding.

...which all goes to show that;  Many roads lead to Rome, but if and how you get there depends on who is driving the chariot!


Once a wire is stripped, operator can think about crimping...

Crimp terminals, Tools, and making a Proper Crimp. 

Crimps were developed as a alternative to soldering...sometimes power is just not available for a an electric soldering iron, and soldering with an open flame in a shop where solvents are also in use, is even less desirable.  A crimp is a good alternative to soldering, and properly made, will give reliable service for a the life of the vehicle.  As with wire strippers above, there are many variations in both Crimp Terminals and also the Tools.  So before attempting to make a connection, it is a good idea to inspect both to see what accommodations or special factors or techniques the operator must be aware of. 

Crimp Terminal Styles:  

Best:  Continuous circular barrel in the crimped area.

Ideally, this is what crimps should look like under the insulation...the seam, where the flat stock meets, is brazed together to make a continuous barrel...it might be worth sacrificially cutting some crimps apart to inform oneself of their internal construction!

The better quality nylon insulated type are identifiable by the translucent, color coded insulator (undoubtedly reflected in a higher price!).  A test crimp with Dimple type crimper will show that the insulation will stand up to this and not be pierced.  With inexpensive crimps that use cheapo plastic, the insulation would be pierced by the Dimple of the crimping operation.   


Formed flat-stock, so a seam is visible, but only under close inspection at the edge of barrel. 

Inexpensive, crimps made from formed, thin tin-plated copper.  These should be inspected to see it the seam has been connected by brazing (good), making the barrel continuous and strong.  If brazed and continuous, the squeeze type dies may be used, but if unconnected at the seam (even cheaper!) along the barrel, the Dimple type crimper or dies should be used, with Dimple positioned opposite seam to assure a good crimp!  The unjoined seam is not strong enough to stand up to the Squeeze type crimper and would splay open, weakening the crimp and lowering the pull-out force. 

Sold as fully insulated...but one also cannot see much of the metal part, so all the cheapness (thin metal and unbrazed seam) are hidden...! 

...one guess as to which types are commonly available on the popular on-line auction site!


Crimping Tools: 

Replaceable dies (many other specialized ones are available), fit into the Paladin crimping tool below.  This allows operator to make squeeze as well as Dimple type crimps, as well as other specialty crimps depending on jaws installed.  This tool is high quality, with a ratcheting action due to the segment gear (at Green) and ratcheting pawl in the handle, which does not allow release of the crimp in the tool, until the jaws have been fully closed.  This, along with the precise dimensions of the dies assures that the full excursion and compression has taken place at the terminal, and removes the operator judgment factor...author calls this action "non-crimpus abortus" (you heard it here first maybe!)...but just in case something goes very wrong, there is a release on the ratcheting pawl.

Higher Price-Range (not highest!) Crimping Tool: 

A small extract of the many crimping dies available for crimping everything from electrical terminals, to cable television coaxial connectors, to telephone or fiber optic terminations:  http://www.lashenelectronics.com/p-1370-paladin-die-sets-for-crimpall8000-1300-series.aspx 

Shown here are jaws which will satisfy most if not all of your automotive crimping needs.  The 2035 set is typically used for the insulated terminals used on SW-EM Kit harnesses.  The 2031 set shows the protruding Dimple pin also found on some inexpensive tools, which can be used on non-insulated (or insulated, with judgment, if they are the cheaper barrel with unjoined seam type!), and the 2033 set would be used for replacement (un-insulated) hex-connector pins seen here:  http://www.sw-em.com/voltage_drop_in_headlights_power_in_hex_connector.htm#replacement_terminals

[Paladin tool info was copied from:  http://www.lashenelectronics.com/p-1370-paladin-die-sets-for-crimpall8000-1300-series.aspx  The author owns the Paladin tool plus several different jaw sets, because of the good performance/cost factor.  This is not intended as a specific endorsement of this tool...many manufacturers produce high quality tools for industrial production environment, which will serve a serious home mechanic for a lifetime. ]

Acceptable crimps can also be made with much less expensive tools, but where the Paladin tool takes just about all of the operator judgment away, the simple, inexpensive tools require the operator to know how much force to apply...on which side of the crimp barrel, and when to release the force.  There is nothing wrong with crimps made with these tools (for automotive duty, although one Rod Collins might disagree with you.  See below:  Info from the boating world), as long as they pass the operator inspection which should follow the crimping operation!  The author has several of these inexpensive tools in various tool boxes around the Embassy!

Mid Price-Range Crimping Tool:  

Typical lineman's or electrician's tool.  A beefy cutter at the tip, and one or or two different sized crimp jaws...operator judgment is required! 

Inexpensive Crimping Tool:  

Multi-tool with crimping for insulated and non-insulated terminals, plus a few other handy functions available...inexpensive, multi-function, and great to have in an emergency toolbox, but again:  Operator judgment is required!...because there a whole bunch of ways to do it wrong with that tool too!  

Making a Proper Crimp:  No matter what Crimping Tool you are using, strip for wire gauge to length for the selected crimp terminal, allowing full insertion into the crimp barrel (with insulation stopping at the barrel, not going into the barrel...point is to crimp onto the conductor, NOT the Insulation!!), and not nicking any strands.  After stripping the stranded wire, and inspecting to assure there is no damage to the conductor, apply just a dab of ACZP onto the stripped conductors before inserting into the crimping barrel, and before applying the crimping force.  The ACZP will displace and surround the wire strands-to-crimp barrel interface, protecting the actual connection from oxidation for a long time and neutralizing any new corrosion which might start.  If a (soldered) Gas-Tight-Joint is the best at wire terminations, this is the next best thing!...and in a harsh automotive environment (especially under the hood), it will serve well, and long, and trouble-free! 


Example of a Poor Crimp:  

Not just one, but multiple strands are hanging in the breeze where they will do nothing in the way of carrying current (this is electrically equivalent of using a smaller gauge wire!).  Also, the stripped wire should have been inserted so that its insulation butts up against the crimp barrel, giving good mechanical support to the wire, and copper strands should be just visible, protruding at the far end of barrel (they are not in the picture).  It is not clear from the picture if the crimp action itself was done adequately without inspection from the other side, but IMO, this is a good example of "Do it Again, and this time, PAY ATTENTION!", and observe all good crimping practices!. 

Notice also, that this crimp has no insulated sleeve covering the junction of crimp barrel and wire insulation end.  That means there is no strain relief of the stresses occurring in this area, so the wire must be well-supported close-by to prevent any movement or vibration from breaking the conductors at the weakened area.  With insulated crimps, where a sleeve supports the junction and thus relieves the strains somewhat, support of the wire can be further away.  [Details, details!]

This is part of a picture harvested from the VW forum, where I haven't yet converted them to also dip the wire in ACZP before inserting it into the barrel.  Maybe eventually they'll learn...!

Notes on a "Good Crimp": 

A search results in countless pictures, and many of these are of cross-sections of crimps made with expensive industrial production, automated crimpers.  That's great and it allows the casual automotive electrician a look at the near-ideal result these machines can produce...but when it comes to needing a few reliable connections to be made on our vehicle, using crimps and tools available retail, we must made due manually, and with a lower level of technology and materials.  This is where knowing whats important, and how to achieve it manually comes in. 

The general rules are that all stripped (but not nicked!) strands are captured in the crimp area, that ideally the deformation of barrel around the strands captures the strands without too much space left over (which decreases the capturing force and allows "pull-out").  Selecting the size and purpose-appropriate crimp and inspecting the result is left to the operator...

Cross-section of a near-perfect crimp (made with an expensive roll-style crimping tool.



Conclusion:  One can see there are a number of places the operator must be aware of in order to get the simple operation of crimping a terminal onto a wire, right...it's not rocket science, but carelessness will definitely affect your effectiveness and reliability in the end...and one can be assured that people building rockets and aerospace equipment observe all of the above mentioned factors (and then some!), including inspecting each step by an inspector other than the operator!  Out in the garage, we are both operator and inspector...I wish:  Good Crimping! 

Good reference information:  http://www.pinrepair.com/connect/

More really good Information about Wiring and Crimps from the Boating World:  https://marinehowto.com/marine-wire-termination/  Independent marine specialist Mr. Collins clearly knows his stuff (electrical, as well as boating specific!), and goes into even more detail than shown here, because proper, reliable wiring is even more important in the boating world, where a failure means you might be stuck in the middle of the lake, or even ocean...but he has not yet discovered ACZP (I wrote him and made him aware of it...and if he ever finds the time to write me back, I'll send him a sample of it!  I expect once he uses it, that he will very much appreciate the fact that it will prevent the growth of green copper oxide corrosion on electrical connections in service in a marine environment!).  


The Lineman's splice (originally developed by Western Union)...when strung between two poles, as far as being able to be put under tension, the end-result is equivalent to a continuous, unmolested wire!  When protected with two layers of heat-shrink tubing under the hood of a vintage Volvo, can be forgotten about because it is every bit as good as an uninterrupted wire.  The Lineman's splice can be used on stranded as well as solid conductors (not that any solid conductors should ever be found in an automobile). 


1.  Strip Wire, generously, with no nicks in conductor!!  (Add two pieces of Heat-Shrink tubing, for shrinking in Step 5, cut to staggered lengths as shown.)

2.  Join Conductors by twisting, evenly, starting at about the middle of the stripped area! 

3.  Add 3-5 further tight turns (That is taken directly from the WU instructions, but on the low side of that is really OK, and perfectly adequate when these wires are not hanging between two poles, under constant tension and exposed to buffeting by the weather!)

4.  Trim, and solder (see below!)

5.  Shrink tubing, with staggered overlap. (Using clear HS tubing allows optional future inspection.  HS tubing also mechanically supports the wire which is now more rigid due to the soldering operation.) 

6.  Forget about splice!  (End-product is equivalent to a continuous, unmolested wire!)



A "tack-soldered" joint where in addition to making the intimate electrical between two wires, the solder is also expected to do the mechanical work of holding them together.  Solder has little mechanical strength(!), especially with vibration input, so this may be OK on the bench or for quick test purposes, but otherwise BAAAD and unacceptable, and not allowed in critical applications (like the vibration environment of a vehicle), I DON'T CARE if this is mechanically supported by Heat-Shrink tubing!  Use a Lineman's splice instead!


Example of a permanent wire repair using the superior Lineman's Splice:  

Splicing and double heat-shrink tubing protection of wiring harness completes a permanent repair.  Color changes apparent are due to variations in production years of harness, and could not be avoided.
Source:  http://www.sw-em.com/740_harness_meltdown.htm    


Look what I ran across...:  

Nothing new (we used a variation of this product in the avionics industry 30 years ago!), but now available inexpensively to mere mortals on the open market.  This is not a specific endorsement of this product, but the concept is most certainly sound...I'll have to get some in my little hands and try them...watch this space for a "Product Review".




Frame capture from their video.


My comments to this product:  " This concept is sound, and has been around for 30 years (we used a similar heat-shrink with internal solder ferrule for a one step, wire-to-terminal termination plus insulated protection, in avionics at that time), but when connecting two wires, simply sticking the wires together as shown in the video is not the best practice...the two wires should come together in a "Lineman's Splice" ...then the tubing slid over with solder ferrule over wires, and activated with heat.  This gives the mechanical joint the strength in tension, of an unmolested wire.  [With this product, support of the wiring (for longer runs, inside a sleeving) is important to prevent any tension to be transferred to the solder joint.]


Notes on Making In-Line Connections:

It's always preferable to make connections to wires at an end, but sometimes, this is just not practical or possible...so when making the necessary connections to existing wires in the middle of a run, or in-line, for a reliable connection, crimp connection to the middle of an existing cable.  I recommend using butt crimps to restore the connection, and adding the new wire.   Best practice when crimping a wire is to cut, and strip the wire, apply ACZP to the stripped strands, and crimp them into a proper butt crimp of the correct size-range for the wire gauge (taking into account that the one side will have more strands because of the added wire), using a quality crimping tool...of course, when I want the absolute best and most permanent, reliable crimped connection I can make, I solder it !! (then protect with double heat shrink tubing)...because there's just no beating a Gas-Tight-Joint!  See also:  740_harness_meltdown.htm#permanent_wiring_repars

I recommend very much against the Scotchlok clip-on, Insulation Displacement Connectors (IDC) [IDC is not the actual issue...the cutting into the conductor which goes along with this style of connector class IS] shown below, also known amusingly as "Strom-Diebe" (Current-Thieves) by the Germans (maybe because it reminds them of the way we tapped into the Russian's telephone line running under East Berlin during the Cold War.  See the fascinating story of:  Operation Gold  or Turning a Cold War Scheme into Reality   ...in any case, see below for my explanation of why these are a "Scourge upon the automotive electrical land!", and should never be used.

...because I totally agree with it, I will also show this picture I saw on Bill Pollack's site...: 

Excerpt from my entry on Tom Bryant's Blog:  https://thosbryant.wordpress.com/2014/06/28/saturn-fuse-box-repair-1998-1999-redux/
 (yellow highlights are not a part of my original post but added for emphasis):

"I don’t agree with your positive assessment of the “Clip-On” [Schotchlok] connectors you show. They work by cutting and displacing wire insulation. Unfortunately, they also cut into the conductor (they’re actually designed to, with a sharp edge and an undersized slot for the conductor), so they are also damaging the conductor and decreasing its cross-section (BAAAAD) [to say nothing of the potential damage in the form of stress-riser they are without a doubt adding to the conductor...and that in a vibration environment!!  Egad!!]. They are merely OK (short-term) under laboratory conditions only (clean, dry, non-moving), but in a vehicle (and long-term), the connection they make is totally susceptible to moisture, and vibration – at least!  I REFUSE to use them…I throw them out (and I don’t throw ANYTHING out), and I replace them when I run across them. 

Again my rule is: If I want the BEST crimp connection I can get…I SOLDER IT(!), so functionally, I’m OK with your solder/shoegoo technique of adding a connection in the middle of a wire, but for a cleaner final appearance, I would use heat-shrink tubing immediately over [freshly applied] silicon RTV (which had not cured). As the tubing shrinks, it compresses the fluid RTV around the insulation, effectively resealing it completely (just as your goo does)…only a bit neater.
If you must make a permanent connection with very good reliability (only second to the soldered connection) to a wire with no access to its terminations (the preferred place for adding a connection!), and also no ability to solder, cut wire, strip both ends, add new stripped wire, crimp into butt-crimp (suitable for gauge of double wire) after dipping twisted strands into ACZP (see:  http://www.sw-em.com/anti_corrosive_paste.htm ).  Additional protection by heat shrink is optional. " 


Shown below, from:  http://www.powerboxer.de/elektrik/66-stromklau  ...a BMW motorcycle enthusiast site, a graphic of why NOT to use these little electrical land-mines-in-waiting.  Their function is based on first cutting through the insulation, then into the stranded conductor (YIKES!  Cutting into or simply nicking  the conductor is one of the first BIG NO-NOs anybody having anything to do with electricity learns about...and that in a vibration environment!!  No thank you!).  Graphic is in German, and he calls it Stromklau - a variation on "Electrical Thief", but even non-German speakers will get a lot from the graphics showing how critical dimensions of the wire are for these to work at all... 

Conductors are shown as a solid orange (1) and this is not really correct...this is oversimplified...a solid conductor would not be able to flatten its shape as shown (2, 3) for this connection strategy to work at all.  Conductor should be shown as multi-stranded type (added better and more detailed graphic below!), so that as it is forced into the connection slot, slot splays open a bit under the force, strands also rearrange a bit into the available reduced space, and those conductors contacted by the sharp edges as the conductor is pressed into place are actually cut and weakened.  Add some vibration, and you can guess the inevitable outcome!

Scotchloks are available for different wire gauges, but 4, 5, 6 below show how conductor OD is critical to allow this concept to work at all...at 4, conductor OD is too big to force into the available slot (it would result in some combination of splaying the contact slot open, as well as cutting the conductor...a mechanical mess with unpredictable long-term electrical function!), at 5, conductor is marginally too small resulting in a contact with low cross-sectional area (poor current handling capability!), and possibly intermittency, finally at 6, conductor is much too small resulting in not fully cutting through insulation in the first place, resulting in highly probable intermittent operation!  With that many possible ways to fail, both short and long-term, the reader can see why I hate them...

 Source:  http://www.powerboxer.de/elektrik/66-stromklau   My mark-ups.

Here is a more detailed diagram of what happens when using Insulation Displacement Connectors...you get the cut conductor strands for free immediately (...bad!), and Lord only knows what in the future (...even worse!)! 

IDCs are for weenies who don't know how to solder or make a proper crimp connection (see above!)...they should never, ever, ever be used in a vibration environment...you have been warned!!


This shows another style of Insulation Displacement Connector taps for "T"ing a wire onto an existing one, which Scott H. found when he investigated intermittent Tail-lighting on his 1800.  This was for lighting of a trailer-hitch (he notes, likely dealer installed). The British Bullet style connectors are used (like in the rest of the 1800 harness).  Scott Hardy pictures used with his kind permission. 


My e-mail comments to these connectors: 

"...those cable taps are also of the Insulation Displacement type, [they pierce the insulation with barbs which then continue to make contact with the conductor] so they probably were installed by the dealer doing the trailer hitch, and they probably did work OK for a while...maybe even years, but ID Conns and wire taps typically only have a very limited contact area, so if the vibration doesn't getcha, the corrosion on that tiny area will eventually...and they might have even worked to this day IF they had been installed gooped up and [protected] with ACZP...!" 

[Bottom line is...if you don't want them to let you down, and have to muck with them in the future, stay away from them also! 

 Insulation Displacement Connectors are for WEENIES!  


Soldering Notes:  Practice helps(!)...the author has been soldering for decades [not a brag!]...from Starter Motor Brush wires in a Volvo, to micro-miniature aerospace Surface Mount Devices under a microscope (where the work area for a half day's work was the size of a Pinky nail!), with superheated air or a 25W iron, to Amazon brass Radiator, Heater Core, or Fuel Tank repairs or Copper Gutters with a 250W iron or even water supply lines [or a Window Lift Cable Ferrule!] with a MAPP Gas torch...so it comes rather easy for me...the intent is not to brag, but this extensive experience allows me to state that the rules and techniques for soldering at a micro-small to huge size, are essentially...no precisely, the same!...first, the base metals must be capable of "taking"  solder (a simplified word which means that solder intimately wets, bonds and flows onto to the base metal, making intimate molecular contact, not all metals do!...Copper and Brass, an alloy of Copper, allow soldering quite well, but so does Steel or tin plate steel of, for instance, a fuel tank!), absolutely clean, and during the actual soldering operation, sufficiently heated to allow the solder to wick into between the various elements of the joint.  Some practical soldering notes follow, and it applies to Volvo wires, as well as Gutters(!).   

See also:  Preparing for Soldering in Amazon Rear Light Fixture Restoration Tech Article.   

Elements to be soldered should be clean of oxidation and/or contamination.  Abrading them immediately before the soldering operation will absolutely assure this!  Flux (in combination with heat) either applied separately or in the form or "Flux-Core Solder" cleans off small residual amounts of surface contamination, preparing the joint...it also increases the surface tension of molten solder promoting its creepage into crevices and around elements to be soldered.  It is not possible to solder successfully without flux! (...sure, one can try, but the result will inevitably be spherical blobs of solder dropped onto the area...not a "Solder Joint", where solder "wets" the surfaces intimately, and flows between them making a Gas-Tight-Joint (sound familiar?). 

Apply flux (or use a "flux core solder"), then using a clean and tinned soldering iron of the appropriate heat range, heat the joint, first, with as good a thermal contact possible on as many of the separate wires or components possible, then bring in the solder into the iron/joint junction, which results in the solder almost immediately melting (and this helps with transferring even more heat) and hopefully being wicked into the joint.  This wicking is what one should watch for(!) and it will not occur if there is is not yet sufficient heat in the joint, and it is not above solder melting temp [Not Heated Long Enough!], or it is still slightly contaminated...so if solder does not wick in, keep the iron in place and allow further heating, and flux to do it's job...maybe applying a bit more flux and solder to help with heating/cleaning...once the wicking is observed to occur between all elements of the joint, [Heated Long Enough!...the Goldilocks point!] it is not necessary to keep applying heat to the joint after that...all the important action is done!  As a matter of fact, operator can, and should, remove the heat-source at the point it has been recognized that flow has occurred between all elements, tying them together with solder....and at that point, knowing you have a good joint, and because if you have not cooked away the flux, the surface tension of the molten solder will result in an almost pleasant looking concave joint (meniscus) in the corners of the joint.  After removing the soldering iron, it is important not to move any of the elements of the joint while solder returns to its solid state (this can cause loss of the intimate bond of solder to the base metals, and a "Cold Joint", identifiable by a dull surface or visible fractures in the solder). 

Contrast that to continuing to apply heat for too long...it is just not necessary to remain on the joint with the iron for long after you observe the solder being wicked into the joint by capillary action.  If, when you pull away, you pull a small peak of solder (convex) with the iron, it means that you've cooked away all of the flux [Heated Too Long!], and this results in loss of surface tension on the molten solder, which in-turn allows the molten solder to stay attached to the iron as it is moved away, pulling a peak.  A solder joint with a peak would be unacceptable in electronics (and anywhere for that matter!), because the wetting to the elements may also be compromised...correct the condition with a quick dab of flux and "reflowing"...this will quickly bring the preferred concave result. 

Separate flux application and using plain solder wire is fine, but "flux core solder" is also available in various gauges.  This is nice because it applies the flux at the same time as the solder, so there is less time for it to cook away.  Using electronic solder is good because the flux is non-corrosive and doesn't necessarily need to be cleaned off like the more aggressive (acidic) plumbing fluxes. 

Too much solder?  Sometimes, due to positioning of the junction or positioning attitude of the junction, and continued adding of solder, a blob might make its way to the lowest point, or even drop off...solder which drops off by itself because gravitational forces on the molten droplet overcome capillary forces was never destined to be a part of the final joint, but it surely helped get the joint ready.  Try to minimize the gaps between joint elements when preparing for soldering, to increase capillary holding force.  Any droplets which form but do not fall away, can be encouraged to fall by holding the soldering iron below the drop...this will cause solder drop to wick onto soldering iron and away from the joint, leaving that concave lower surface.

See also:  Important Reference Information for Soldering

(Pre)-Tinning Soldered Connections:  "Tinning" is a solder-preparation process by which the separate elements of a joint to be soldered are first heated and get a small amount of solder applied. This brings with it a number of advantages...it allows a close inspection of the solder wicking and flowing action as the elements are separate and not in-part covering and obscuring each other (possibly allowing a no-flow, bad joint) condition to go un-noticed, and it also assists and assures heat-transfer and solder flow in the next step.

After all elements (or just the elements which "needed a little help") have been tinned, they are united in the final position and heat is once again added (the tinning improving heat transfer!) to allow solder to "reflow", and a bit more can be added, to fill any remaining voids between elements, again targeting a nice concave meniscus of solder in corners...no balls or warts of excess solder allowed!

An example of assuring a perfect solder Joint (Gas-Tight!) using tinning is rework of the 122(544-12V) Fuseblock.  See also:  http://www.sw-em.com/gastight.htm    After the brass plates are pre-cleaned by media blasting, they are tinned before being reassembled in-place, then reheated as torque is added to the brass fastener (to allow the fastener to compress the stack with only minimal solder in between the plates). Simply soldering without tinning preparation would not assure the gas-tight condition between plates.  The Tinning and reflowing processing results in turning the stack of contacts into a monolithic conductive structure with absolutely the minimum resistance now and pretty much forever more!!  [Not to make too a big deal of this, but this structure is now ideal and the very best it can be electrically speaking...short-term, and long-term!]

Rant about Digital Solder Stations and (communist plot!) no-lead solder.

The temperature controlled soldering stations with fancy digital readout, are in my opinion completely disco-bullshit and unnecessary for an operator who knows how to solder...meaning they know what to watch for, what to do, and when!  By temperature controlling (what I would more correctly describe as limiting the tip at some temperature in these fancy solder stations), they have once again tried to take the operator judgment out of the operation, to the detriment of the process and often final result, because proper soldering technique simply requires operator to do certain things correctly, and no digital readout is going to correct improper technique, or conversely, ensure proper soldering technique!! 

This digital BS is undoubtedly in response to the (communist plot!) no-lead solders which don't flow as well or recognizably as the lead alloy eutectic solders.  By limiting the iron temperature, they limit the heat operator can put into a joint while they are waiting for the (communist plot!) no-lead solder to flow.  This in contrast to using a hotter iron properly, putting heat into the joint and recognizing when the lead-alloy solder flows, as it inevitably must and will, as soon as it has reached its melting temperature!  [The flowing solder is the temperature indicator!!...hey...here's a concept!]

Part of proper soldering technique means recognizing when the solder melts and flows...THAT is the indication to the skilled operator that sufficient heat has been put into the joint, because THAT is what the operator should be looking for, THAT is the moment when heat is sufficient to melt and flow/wick solder to assure a proper joint, and heatsource may be removed when sufficient flow has been verified, and this is a function of the operator, not some abstract number the dial has been set to...what does that number have to do with recognizing a proper joint??  ...very little!  SEEING it melt and flow on the other hand is unmistakable, but it is the operator's responsibility, and that cannot be removed from the operation!!  The operator must still observe WHEN the solder melts and flows, and only after that may the heatsource be removed anyway!  The problem once again goes back to 1.  ...trying to remove operator technique and ability, so that less expensive, less well trained operators can be employed and 2. ...the (communist plot!) no-lead solder which is not as easily recognizable as having begun to flow, so it becomes necessary to limit the amount of heat an inexperienced operator can put into a joint because they may not as easily recognize when the (communist plot!) no-lead solder has flowed and so would tend to leave the heatsource in place while waiting for this to happen, overheating the area.   

What does the impressive digital number on a soldering station do???...nothing(!), but limit the heat available so that the soldering iron tip must be held onto the joint even LONGER, possibly cooking sensitive components or a substrate.  Bottom line and my position is... I want MORE heat, not less heat(!), because I know when to remove it!!  I could if necessary, solder an Surface Mount Component with a 300W gutter soldering iron without damaging it or the surrounding area, because I know what to look for, and THAT operator judgment, and not artificially limited equipment, will keep me from creating collateral damage!! 

Keep your digital readout solder stations!  I'll keep my wonderful functioning,  Weller TCPN solder station (actually also thermomagnetically temperature controlled!), gratefully accepted from a former employer when they were convinced to throw out all their solder stations and "upgrade" to the super groovy, and totally unnecessary, digital horsepockey stations! 

Weller TCPN Solder Station using the thermomagnetic tips.  TC201 Solder Tips

Lead Poisoning?...Hogwash!  Finally, the smoke coming off a solder joint as you're soldering is from the flux cooking off, and not from the lead, so relax about any alleged dangers from lead fumes!  The melting point of eutectic (electronic lead-tin alloy) solder is around 390DegF, and while your soldering iron is even heating it up somewhat above that, it is still WAAAAY below the 3180DegF boiling temp of lead, needed to release the (deadly) lead fumes.  Sure, the odd molecule of lead might be released (water releases molecules and evaporates at room, and even frozen temps too!), but there is a higher danger to the solderer from exposure to cosmic radiation from the Kuiper Belt than from those few lead molecules maybe being liberated!  Safety concerns of lead fumes from soldering are completely overblown by safety nannies who attended Basket-Weaving or Women's Studies classes in school, instead of Physics and Chemistry, where they might possibly have learned about properties of materials in the real world, and how things made of them work!  A little fan to dissipate the (not so deadly) smoke, so you can see what you're doing at the joint, will help!   

Lead-Free Solder Sucks!:  

Having worked in industries from military electronics, avionics, to industrial and commercial electronics, not to mention as a private inventor and licensed radio amateur, the author has made many solder joints varying in size and base materials, using various solder formulations, and analyzed many a solder joint failure also, so I am qualified in making this statement!  Here is some information to substantiate this: 

Notes:  Non-Corrosive Flux for Lead-Tin solder vs. Corrosive Flux for No-Lead solder.  Formation of Tin Whiskers in non-Lead Solder. 

An excerpt from the article:  Understanding and Mitigating Tin Whiskers by John O’Boyle, Maxim Integrated Products
Reference:  https://www.eetimes.com/document.asp?doc_id=1279227

"  Recall that the expected environmental harm from lead in electronics was the impetus behind the RoHS legislative action. Lead was feared as a contaminant to groundwater. Many well-intentioned people overlook one important fact, however: Elemental lead is not water soluble. Other sources concur: "Lead does not break down in the environment. Once lead falls onto soil, it usually sticks to the soil particles."5 When burned in an open-fire recycling operation, lead was feared to cause a poisonous vapor if inhaled. From NASA6, the facts are:

  1. An open-fire temperature is approximately 1000°C, but lead boils at 1740°C.
  2. Thus, the vapor pressure of lead would be negligible, presenting little possibility of lead-vapor poisoning.
  3. Workers who solder with tin lead (SnPb) solder do not have high lead levels in their blood.
In the end, there is no evidence that lead in electronics presents a health risk or causes environmental harm. Ironically, many of the proposed lead-free solutions do pose environment problems and many are much worse for the environment. "

See also Vid:  Are Soldering Fumes Dangerous?:  https://www.youtube.com/watch?v=EGdlM48eDbA

Good info comparing lead-based to non-lead (communist plot and scourge) solder:  https://www.youtube.com/watch?v=reNA5iwcg-w

My comments to that vid:  "You are absolutely right...and give very good objective scientific information indeed!...unfortunately being associated with RC modeling, it might not be taken as seriously as it should...I too was tempted to not watch the vid to the end, but am glad I did! The "environmental issues" you mention, and the reasons for removing lead from solder is the European RoHs and is based on BS substantiations (see Ref!): ...that there is some massive exposure to lead in electronics, when in reality the amount used there is absolutely minuscule compared to the amount used in lead-acid car batteries (which are EXEMPT from these regulations...because its tough to make a lead-acid battery without lead!)...so here we are...
Lead-free solder does absolutely SUCK! ...from a use and effectiveness standpoints (more corrosive fluxes are required, which can corrode electronics if not cleaned off well, much more difficult to use and get a good joint, etc), also from a negative side-effect standpoint (tin whiskers are a serious reliability issue, especially in High-Rel like military and aerospace!)
The fact that ebay suppliers of counterfeit china-crap goods don't know how to tell 1mm from 0.8mm, and lead-tin from no lead, or maybe they do and think the customers are too stupid to notice this...and the fact that those pricks could f**k up a junkyard, is a different issue... You should send that useless crap solder back to the thieves, and let them eat it...its not poisonous!
Reference:  eetimes.com/doc?asp_id=1279227  Cheers  "

Link to Whiskers (metallurgy)https://en.wikipedia.org/wiki/Whisker_(metallurgy)


Practical Applications of Soldering, as Applied on a Vintage Volvo: 

Sometimes the soldered joint is electrical, sometimes it's mechanical, sometimes both...

(Re)soldering Window Lift Cable on a 122:

The Window Lift Sprocket Chain, which is positively moved by the Window Crank Sprocket, transitions to a simple steel cable, then secured to the Window Frame by means of a soldered Ferrule.  Solder is not generally a good junction suitable for transferring mechanical (in this case:  Shear), but it is my thought that this 1+ inch long joint was intended to limit the maximum force, and slip if it was ever exceeded, preventing damage to other components of the assembly.  A common failure mode is that the intimate bond between steel wire, and solder releases with time having weakened the joint such that it fails at a much lower force level than originally designed.  Resoldering the joint is the simple solution!    

Andrew Nance pic reposted with his kind permission. 

Window lift cable is united with a Ferrule by soldering, and the Ferrule is in-turn secured to the Window frame with a clamp.  This solder joint is a force limited connection where occasionally the intimate solder bond releases after many years and countless transfers of the window lifting tension.  This connection allows transfer of high force, and simple manufacture and adjustment at time of manufacture!, and also a force limiting factor.  Occasionally, the solder separates from the steel cable (as is the case here) and Window falls into the door, but the repair is simple!


Excerpt from a Thread:
My original recommendation was to reflow the solder-joint at the Ferrule.


Andrew:  "I tried to heat it and I can’t get it hot enough to re-melt."  [...under the same principle of "Don't use force...get a bigger Hammer!":  Don't use a Bic lighter, use a Bernzomatic torch!]

My Response:  "You've got the right idea...clean area where it needs to be soldered, add flux [not plumbing acidic, but electronic rosin!] there, move it into position in ferrule, then reheat with a torch, if necessary, use hotter MAPP gas, (but I don't believe I needed that last time I had to do this job), and reflow solder, add new (electronic rosin core!) to help with solder flowing. Be sure to shield glass from heat."  [Reflowing the solder will reestablish its bond with the wire for another 50 years probably!]

...and several well-meaning guys chimed in with other permanent cable solution suggestions...

My Response:  "With permanent mechanical solutions like cable-stops, clamps and crimps, lost is the safety factor of it releasing if and when too much force is applied. This protects other parts of the lift mechanism from more serious damage! Unfortunately and occasionally, as here, the solder joint can also releases due to age, and not not necessarily the application of overforce, but I still recommend against all of those non-standard repairs mentioned! Do not second guess Volvo's designers and engineers with some sort of quick-fix hacks! 

Just resolder the darn thing, retaining the designed-in safety factor and it will last another 50 years!"


Solution:  Apparently Andrew was pressed for time, so replaced the Cable with new.  He offered to donate it to the SW-EM Science Department.


PLACEHOLDER FOR RESULTS OF REPAIR  [Tech ArticleWindow Lift Cable Repair ]



Reference Information: 

Exploded assembly diagram of an Amazon door. 

In this exploded assembly, I have completed the routing of the window lift Wire and Sprocket and Chain in Blue, and highlighted the area of interest in Orange.


140 Instrument Panel Repair by Soldering Swaged Pins:  

Soldering to the rescue!  My response to a thread about intermittent and strange symptoms associated with a connector on the back of a 140 Instrument Panel.  This connector plugs into pins in the Printed Circuit Board of the Inst Panel, which are swaged into the PCB.  This manner of securing the pins was OK initially, but in the long-term, especially exposed to the thermal cycling of a vehicular instrument panel, has been shown to have a weakness. 


Excerpt from original posting:  "...The problem is that the temperature gauge does not work the way it should be working. The temperature gauge only works If i remove the red marked connector from the instrument AND turn the lights on. If i either turn the lights of or put the connector back then the temperature gauge stops working.  !!!HELP!!!  "  [...sounds like "two wrongs make a right" again!]


My response:  "I don't think it's the connector itself, but it's the associated pins on on the Inst Panel Printed Circuit Board !...because that looks quite familiar...and the odd symptoms are suggestive of an (or multiple) open pin(s) leading to the tying together of normally unrelated circuits. [and/or unusual current paths!]


...a long time ago Gretchen and Dave Adams' 240 instrument panel had intermittent issues which went away after I simply soldered all those pins to their respective conductor (on the side of PCB not shown...these pins are swaged into the PCB, a process which can stand only a limited number of thermal cycles!)...then the corner of the pin looses contact to the copper trace after those [countless] thermal cycles.

Soldering permanently bridges the connection which opens...this will obviously require careful further disassembly to access to the other side of PCB, and should be done by a qualified electronics technician who knows how to prep and solder.[...and who knows which end of the soldering iron to hold, see:  Important Reference Information!] 

I can't guarantee success, but it has worked before and that is where I would recommend repair attempts begin!  Thankfully, the 140 Inst Panel is not too huge of a job to replace and test, should this not sort the issue.
Please let me know how you make out, and I request you document this operation well, as I never did (it was looong before digital cameras were in everyone's pocket!), but I would like to add it to this soldering page as a good example of how soldering is a permanent repair for production techniques with limited service life.  Cheers"


Jan Piening pictures permission to repost granted.   

Business side of the 140 Inst Panel (Phenolic Printed Circuit Board) with multiple swaged-in pins evident.  Wired component is the (5.1V) Voltage Stabilizer of fame and lore. 



View when tilting Instrument Cluster back and before disconnecting highlighted connector, which Jan thought might be responsible for the issues.




Swaged Printed Circuit Board Pins Explained:


Cross-section of the brass interconnect pins in various states on a Printed Circuit Board.  During the installation procedure, the tubular barrel is swaged open and flat (to some degree or another, production process and tolerances dependent!) against the Blue copper conductor on the PCB.  Unfortunately this electro-mechanical joint is of relatively small flat area (and at the corner of the hole), is also subject to thermal jacking and corrosion, which eventually leads to intermittents and opens.  By soldering the pin to the conductor, with solder bridging this formerly relatively small and electrically susceptible area, solder intimately wets both pin and conductor copper with a comparatively huge gas-tight-solder-joint which can stand up very well to thermal cycling.   


Note:  The above explanation applies to the single conductor sided, phenolic base material as found in the vintage Volvos only, not later developments of the technology, featuring double sided PCBs, and plated-through holes, which were much less susceptible to the issue presented here.  ...but not exempt and immune!  Link to a related thread - Volvo Electrical Instrument Panel Repair on VOC site:  https://www.volvoclub.org.uk/faq/ElectricalInstrumentsPanelRepair.htm



Volvo Amazon Fuel Tank Filler Leak Repair by Soldering: 


Link to:  https://www.sw-em.com/Fuel_Tank_Notes.htm#Common_Fuel_Tank_Issues



Important Reference Information for Soldering: 


External sources are attributed where possible.  Otherwise this information is Copyright © 2018-2022.  Ronald Kwas.   The terms Volvo, Paladin, Weller are used for reference only.  I have no affiliation with any of these companies, other than to try to keep their products working for me, help other enthusiasts do the same, and also present my highly opinionated results of the use of their products here.  The information presented comes from my own experience and carefully considered opinion, and can be used (or not!), or ridiculed and laughed at around the watercooler, or worshipped, at the readers discretion...and lead-free solder really does suck!  As with any recipe, your results may vary, and you are, and will always be, in charge of your own knuckles and future!


You are welcome to use the information here in good health, and for your own non-commercial purposes, but if you reprint or otherwise republish this article, you must give credit to the author or link back to the SwEm site as the source.  If you don’t, you’re just a lazy, scum sucking plagiarist, and the Boston Globe wants you!  As always, if you can supply corrections, or additional objective information or experience, I will always consider it, and consider working it into the next revision of this article...along with likely the odd and unique metaphor and probably wise-a** comment. 


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