Wiring Notes and Related
Mar 2018 R. Kwas Revisions on-going [Additional Comments]
Wire Gauge vs Current
The Lowly .250" Push-On Terminal
Crimp terminals, Tools, and making a Proper Crimp
The Lineman's splice
Notes on Making In-Line Connections
Wire Gauge vs Current
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!"
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!)]
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 Crimpers:
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. This is the only stripper I would use when wiring an aircraft!
Squeezing the handle both cuts insulation, then pulls it away. 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 above as those remove operator error, and possibility of nicking a conductor! In these strippers, 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 result. Good for 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 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.
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 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 (uninsulated 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 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 apart to inform oneself!
The better quality nylon insulated type are identifiable by the translucent insulator (as well as a likely 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.
Formed flat-stock, so a seam is visible 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!
Replicable 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 (uninsulated) 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 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!
Making a Proper Crimp: Strip for wire gauge to length for the selected crimp terminal, allowing full insertion into the crimp barrel (with insulation stopping at the barrel...point is to crimp onto the conductor, NOT the Insulation!!), 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 it from oxidation for a long time...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!
PLACEHOLDER FOR EXAMPLES OF GOOD AND BAD CRIMPS
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 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 as good as an uninterrupted wire. 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 when these wires are not hanging between two poles and 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!)
Example of a permanent wire repair using a 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.
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 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) 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:
(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 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. 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, and Lord knows what in the future!
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!!
Soldering Notes: Practice helps(!)...the author has been soldering for decades...from Starter Brush wires in a Volvo, to micro-miniature Surface Mount Devices under a microscope, with superheated air or a 25W iron, to Radiator, or Fuel Tank repairs or Copper Gutters with a 250W iron or even water supply lines with a torch...so it comes rather easy for me...I don't mean to brag, but this experience allows me to state that the rules and techniques are essentially the same...first, the base metals must be capable of taking solder (not all metals do!), 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, or Gutters(!):
Elements to be soldered should be clean of oxidation and/or contamination. Flux 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!).
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...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 of 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 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, 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 plumbing fluxes.
Lead Poisoning?...Hogwash! Finally, the smoke coming off a solder joint as you're soldering is from the flux, 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 may even be heating it up way above that, it is still WAAAAY below the 3000DegF 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 temps too!), but there is a higher danger to the solderer from exposure to cosmic radiation from the Kuiper Belt than from those few 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, 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!
External sources are attributed where possible. Otherwise this information is Copyright © 2018. Ronald Kwas. The term Volvo is used for reference only. I have no affiliation with this company, other than to try to keep its 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. As with any recipe, your results may vary, and you are, and will always be, in charge of your own knuckles!
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 metaphor and probably wise-a** comment.