The Gas-Tight-Joint
R.Kwas  Original 12/00,Revisions on-going.

Reference Information
    I2R Heating


This is another installment of Electrical Ramblings in which I thought I'd go a bit further into a cause of frustrating failures of electricals, corrosion. Generally, when I work on vehicles I always prefer the long term fix to the Q&D (Quick and Dirty), since it means the highest reliability factor and therefore the longest interval until the next time I have to fiddle with the same item. When practically applied to vehicular electrical connections, this principle frequently translates into: Gas-Tight-Joint--no, we're not talking about a new gimmick for potheads, but I'm getting ahead of myself, and I shouldn't detract from the importance of this thing by making dumb jokes! The examples I'll use here are the fuse blocks of the 544/122S and early 1800s. This may seem like ancient history to some readers, but appreciate this: these discussions may be applied to brand new Volvos as preventive measures, just as I present them here for purposes of repair/restoration.

An electrical connection by definition means making a contact between two pieces of metal. In a car, especially under the hood--dust, rain water and salt-containing winter slush serve to make a pretty poor environment for these connections, with corrosion or dirt eventually occupying between the contacts. You may note that many important connectors such as of the Bosch injection, have a rubber bootie to protect against contamination. But as these booties are seldom air tight, in the long run, moisture containing air still enters to promote corrosion, just as it does on unprotected sheet metal of a car.

Shown are two fuse blocks. On the left, as removed from the vehicle with one rivet drilled out and the stacked brass contacts laid out for inspection. Note the green stuff * (non-scientific term for a confirmed poor conductor, very familiar to any sea going readers, not to be confused with, but having electrical characteristics similar to the green stuff mined from an eight year old's nose), located where we would expect a good contact. No such luck here. This fuse block is a good candidate for rework. We probably had hints of problems with the amp light coming on brighter and brighter with time when we turned on the blower or the final failure where symptoms are similar to a blown #1 fuse. (Full amp light, no gas gauge, but fuse is intact and turning it to clean the contact ends is fruitless--more on this later.)

On the right, a restored fuseblock is shown. Where the contacts have been media blasted, then filed to reveal shiny new metal, tinned (a process of wetting the base metal with flux and solder) and reassembled using brass hardware in place of the original rivet. Heating the whole contact assembly with a soldering iron, applying more solder and tightening the hardware (while keeping everything lined up) completes the process.  An octopus would have a distinct advantage here, but I've gotten pretty adept at it.  What we have made is a Gas-Tight-Joint (a term from connector engineering) where, in this case, the solder makes an intimate, electrically very good, metal to metal contact (and also takes up any free space in the electrical connection preventing the ingress of air/moisture which would act as a corrosion promoting electrolyte...for a damned long time! 


This is not a side an owner might normally or often see their Fuseblock from, but if it looks like this on the surface,
one can presume intertab stack corrosion is well under way, and it's time to consider a Sw-Em Restored/Reworked Fuseblock!

[Would you like to see some more evidence of what happens when passing current through a poor connection?  See Tech article:  An Automotive Electrical Primer ]

We now have a better than new fuseblock for reinstallation, but two other sources of problems need consideration. One area is the conical ends on what I call "Euro-fuses" used on Volvos through the 240 series. These make contact at the conical ends, in two small circles, which are also very susceptible to loss of contact due to green stuff corrosion. If this corrosion happens to be on the fuse protecting the fuel pump power circuit, the results can be car-stopping, or mighty annoying if intermittent...and spinning the fuse to restore the connection is certainly no long term fix either!

...maybe they were making a connection, maybe not!

The last area of concern is the spade terminal connections to the fuseblock of 122s (or just about anywhere else for that matter!).  In both of these cases, the GTJ strategy applies...but since we can't solder these connections, a different implementation is needed.  Simple!  It is just a dab of anti-corrosive** paste (not to be confused with insulating dielectric grease), on all of the spade terminals and fuse ends after clean-up to protect and prevent new corrosion. (If loose, a slight squeeze with a pliers will restore good spring action to the terminal on the wire.)


Since first writing this, I made a much closer inspection of the early 1800 fuse block design.  Absolutely horrendous!  What I found leads me to have even more contempt for Lucas, for their s**t design.  I have since  extracted the 1800 specific information.  You may find it under:  Gas-Tight-Joint Part II - Lucas works (dark) magic on the 1800


Shown below is a Lucas fuseblock (insert your favorite, [well deserved] Lucas slur here) out of an early 1800, with those way-less-than-impressive clips holding (and passing current through - maybe) an original equipment Lucas fuse (insert another slur from your repertoire).  Besides the fact, that an 1800 has a total of three fuses...battery power, ignition power and parking lights?...the logic of this is arguable, but was obviously arrived at after the consumption of possibly several pints of (warm) Guinness (which in itself is not necessarily a problem, but shouldn't directly precede any engineering work intended to stand up later, to any sort of scrutiny).  Clearly, a thorough cleanup of all contact areas followed by application of anti-corrosive paste is called for...see fuseblock on right.

1800 Fuseblock - Before

After...much better!  ...and probably half of all 1800 electrical problems cured and prevented!

In the case of a permanent connection not subject to movement during service, soldering is hard to beat. When using crimp type terminals, coat the stripped wire end with anti-corrosive paste before inserting into the terminal. As the terminal is crimped, the paste will be displaced around the actual contact protecting it with a GTJ. Need another convincing example? Look at the electrical connections on your vehicle’s horns!  I keep telling people that when I retire, I'm going to buy a 55gal. drum of the stuff and set up shop at some salt water marina somewhere...Aruba - yeah, that's it...where the fish are big, the bikinis small, and in between gooping the stuff on electrical connections of peoples' boats, I'll be sitting around drinking Piña Coladas with little umbrellas...that is, when I'm not cruising around the island in probably the only Amazon!  

For almost any large removable connector such as the spade terminals typical on cars or terminals held in place by a nut (yes, including battery terminals), the compound may certainly be used, including those Bosch injection connectors with the rubber booties.  For small or multi-conductor connectors where it may be possible to bridge conductors (thereby possibly shorting or affecting the sensor signals), it is better to clean the contact area with a light abrasive such as a pencil eraser or fine emery board when contact problems are suspected and not use any compound.  [*** see update below]  Gold plated contacts such as found in the throttle position sensing switch of fuel injected cars should be cleaned with alcohol and a Q-tip only--no abrasives, since these can damage the extremely thin gold plating. A while ago, soldering the gold plated pins of the connector on the instrument panel printed circuit board of David and Gretchen Adams' 264 was the presumed cure for a pesky cold-temperature intermittent condition. These pins are swadged into the circuit board. Add a bit of time, moisture, and in this case most important, microscopic but nonetheless relentless movement due to temperature changes and you get a "sometimes connection" possibly dependent on the moon-phase.  GTJ to the rescue here - the problem NEVER recurred after repairs.

A last couple of suggestions for a gas-tight-joint. Bayonet base bulbs such as found in signal/tail light assemblies. Many times a non-working bulb is due again to green stuff and not a burned out bulb. Another important electrical tie point is the 12V supply block on later model Volvos, supplying the injection system among other things. I do need to emphasize that the compound is not the cure to existing corrosion but a preventative to be applied after a proper restoration and clean-up of the contact in question. You get the idea. I'll leave it to the reader to come up with further uses. Go for the long term fix!

Finally, old car electricals are usually due some TLC and with ever-increasingly complicated new car electrical systems, anything we can do to keep corrosion in check will be to our advantage. For those who don't have the ability to do-it-yourself, see SwEm kits section for restored fuseblocks available--even ones restored using GTJ practice and rivets--so the appearance is absolutely stock!  It is also possible to rework fuseblocks to accept the more commonly available 3AG (1/4 dia. X 1 1/4 long, tubular ceramic or glass) fuses.  The cover still fits perfectly on the fuseblock as before, so again the appearance is absolutely stock (until obviously cover is removed), these are available by special arrangement only.

See also:  The Gas-Tight-Joint, Part II,...  


Reference Information: 

I2R Heating:  Poor connections* make heat when current is passed through's the Law! (Ohms!).  See below for an impressive Infra-Red photo of what happens  in industry (but what is indivisible to us without a camera able to see in the Infra-Red spectrum!)...similar overheating of wiring and connections can happen at a smaller scale on a corroded vehicular electrical system, with potentially disastrous results!  (See:  ) 

This can also happen at your house, particularly if you have aluminum might consider a periodic IR thermographic inspection of your electrical distribution panel!  If you don't have an IR videocam, those cute little IR temperature indicators with a laser pointer would do the trick nicely to check an 1800 FuseBlock, and they are coming down to a price which shouldn't keep them out of a well equipped toolbox!  [In between taking temp measurements, I can't help but play Capt. Kirk's Phasor with them...sorry.] 


Kirk IR thermal checking an 1800.

If you're interested further...there's a comprehensive report: Reducing the Fire Hazard in Aluminum-Wired Homes by a Professional Engineer on the subject at this off-site link.  Improperly installed aluminum wiring in houses is BAAAAAD stuff!]). 

* A "Poor Connection" briefly explained:  A connection can become "poor" after having been adequate and fine for a long time after being initially designed to carry a certain (normal) amount of current, and installed.  "Poor" means inadequate for the amount of current flowing, so it may become poor by developing an in-line resistance...this is typically what happens, after time, in our cars, where the connections are under environmental attack, but poor can also mean the connection is passing more current, either because usage at the load has increased, or even because a fault overload current is flowing, and the circuit protective device (fuse or breaker) has not opened to stop the overcurrent.  Shown below is an Infra-Red view of fuses and associated connections, of an industrial power distribution board.  The warm areas of the right and left hand fuses show that there is load current flowing, but the middle fuse, and its connection are generating lots of heat...either due to a "poor" connection (loose/corroded etc.) or an overcurrent.  Further tests are called, IMMEDIATELY(!), for to determine which!

An Infrared image from a Thermographic inspection of an industrial electrical distribution panel.  The color enhancing by temperature makes differences in temperature to the surrounding area tough to miss!  It's the same technology which is used to locate lost hikers from search helicopters, and unconscious people in burning buildings!  Source:


My response to a posting on VW Vanagon forum...  "I did notice the earth lead for the battery getting actually hot"

"  A connection getting hot is an indication that the current passing is more than the condition of the connection can safely pass, meaning a high series Resistance...[Edit Add: I should have mentioned I2R Heating...see:] the connection has loosened or corroded, or (has more current been added to the circuit?) any case, it gives you an important clue as to where to start with a correction! If this is your starter high current, start by disassembling connectors and terminals, checking if they were tight, but inspecting and cleaning/abrading them to shiny metal (also check state and amount of corrosion on crimps!). ALL current carrying surfaces should start this way (as they did when vehicle was first assembled!), then reassemble, anointing all those current carrying surfaces with Anti-Corrosive Zinc Paste (see: ), NOT dielectric grease(!), which will get displaced when terminals and connectors are tightened, encapsulating the connection (so if beneath the vehicle, being soaked wont bother it in the least(!) and chemically neutralizing future corrosion.

Tip: The ENTIRE current carrying path and its connections should be treated preventatively in this manner (and I understand in a Vanagon there are a number of connections along the way (my specific expertise is with vintage Volvos, I am now a Vanagon friend by association) but all info I have given is absolutely applicable, and used, recommended, and proven for decades!)...then you will have reliable function, and good starting, since you will be experiencing as little VDrop from the Batt to the Solenoid/Starter. If you still notice connections heating under certain conditions, inspect for hidden series R, if you cant find anything obviously wrong, adding a parallel conductor is a possibility, but should be a last resort, after making existing connections their best...

To answer your question about cable gauges gas vs diesel...yes they are generally bigger with diesel because not only does Batt supply Starter, it must also supply a fair amount of current to glow-plugs.

Cheers and Good Hunting from the vintage Volvo World!  "

For Early (carbureted 1800) Owners, see:


Shown here is a pretty extreme example of I2R Heating!...the middle connection is developing LOTS of heat...either because it is carrying a normal magnitude of current, and that nut is loose OR the nut is perfectly tight, but it is carrying an abnormally high current...what was a perfectly adequate connection for the normal current, is, or has become inadequate for the higher current! 

Another example of I2R heating, where an IR camera is not necessary...but soon a fire extinguisher will be, after the insulation on the wire catches fire!  Few insulation materials can stand a glowing heat source!  


* Mostly oxides of copper, and definitely a poor electrical conductor.    

**Penetrox is Burndy's trade name for anti-oxidant zinc suspension paste required by electrical codes on aluminum-to-copper connections (the electrical industry figured it out after galvanic corrosion caused by dissimilar metals in contact, in addition to differing coefficients of thermal expansion, resulted in fires which burned down more than a few  houses!  Anti-oxidant pastes are available from a number of manufacturers...Ideal calls their similar product Noalox. Electrical supply places are certain to carry it.  Link to additional info on electrical anti-corrosive paste.  [Off-site link of radio amateur K1TTT to more good info including pricing/sources of these products:  ]  


Update:  ***A terrific new product has become available for cleaning, lubing and long-term protection of delicate connections (from PC boards to tiny pinned connectors to sliding contacts of volume controls or board type position switches.  This product is ideal for the D-Jetronic Throttle Position Switch,  since it leaves a lubing protective film behind after cleaning - just what the switch needs (GTJ to the rescue again!).  Much better than electronic tuner cleaner, which certainly cleaned but left little behind in the way of long-term protection...the stuff is called Deoxit D-5 from (CAIG Laboratories, Inc.), and is available in variable stream spray-cans at electronic supply houses.  I highly recommend it!  See also: 


External material sources are attributed.  Otherwise, this article is Copyright © 2000-2022.  Ronald Kwas.   The terms Volvo, Burndy, CAIG, 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, 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. 


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