"Smoke in the Cockpit!"

Nov 2021 R. Kwas  (Comments Added)

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1800 (Lucas) Footswitch Evaluation
122 (Bosch?) Footswitch Evaluation

I2R Heating in the VW World

Links
    Fuse your Cigarette Lighter!

Reference Information

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A source of pilot stress in an aircraft...and only slightly less in a car!
Image Source:  https://www.ainonline.com 

Although a very rare occurrence aircraft, in cars, it has been known to occur with more frequency (particularly in Lucas equipped early 1800s!)...in either case, it does get ones full attention.  At least we car-drivers can pull to the side of the road immediately to stop engine (Charging Sys is one power source), disconnect the Battery (the other power source), and investigate...or address flames! 

With some good logical and systematic troubleshooting, mostly really just forensic analysis of the aftermath, all actually performed an ocean away, under the author's direction, this P1800 owner in the UK was able to locate and address the source of "Smoke in the Cockpit" (Yikes!).  Link to thread:  Dodgy Wiring, HELP  "My P1800 started smoking from behind the steering wheel today".   http://www.volvoforums.org.uk/showthread.php?t=89108  

I would have liked to republish the pictures of the damage and associated troubleshooting recommendations, but unfortunately, it looks like some of the associated pictures are no longer at the link...I'll see if I can get them and include them here as it is an example of interpreting the forensic evidence, good troubleshooting technique with a successful outcome, which might help another P1800 owner. 

Without having a picture of it, I do recall was the biggest hint...the Blue (18ga.?) wire between Light Switch and Foot Hi/Lo Beam Switch was severely overheated, that it was melted to the extent expected if it was passing current to a chassis short...it was obviously the source of the smoke.  Since this power source wire, coming from the Lightswitch, was the only melted wire on the Footswitch, logical troubleshooting technique implies that the high current flowed to chassis AT the Footswitch, and indeed this had been the case.  

Bottom line and cause of the smoke was two-fold:  The Lucas Footswitch had been previously "repaired" or replaced, and poorly remounted, such that it was loose, and it also did not have an insulated bottom cover, which allowed one of the wire terminals (incoming power) to touch the chassis mounting surface...leading once again to the failure of a Lucas component being visible on IR Sat from space!  See:  Reference Information 

I am in the process of disassembling and reviewing both 122 (Bosch(?) supplied) and 1800 (Lucas supplied) Footswitches, results of which will be published in a Tech Article...watch this space...!

Recapping the Thread:  

"Cynic-al" wrote:  "My P1800 started smoking from behind the steering wheel today..." 

"Home now at least, courtesy of tow-truck, never thought I'd see the day!" 


Electrically stricken 1800 needing rescue on a rainy British night...it looks like the Marker Lights still work! 
Unfortunately, this is the only picture still present on the thread...hey, isn't he parked on the wrong side for the UK...?

Excerpts of my postings to thread:  "Before reconnecting the battery, I'd expend a good amount of effort to try to locate the source of the smoke...including looking at back of dashboard with a good light source (and possibly a mirror) and lightly probing around with an insulated poking tool...also wiping with a cotton swab and sniffing it...once you've located the melted wire or loose terminal, or area damaged by heat, report back with findings. You can also trust the color code to tell you which circuit and load device were involved. I also recommend squaring this issue away before taking any significant drives.

Good Hunting!

PS. It's important when something like this occurs to gather as much associated info...can you associate the smoke with having turned ON any particular load...can you associate the smoke with a gauge (ie fuel, tach) or indicator (Charging Indicator) working or not working or lit or not lit? Were headlights ON at the time? Info like this is often invaluable in locating the problem."

He then posted a picture of the Footswitch (or Lightswitch) showing unmistakable evidence that the Blue wire what carried enough current to melt its insulation, making lots of acrid "Smoke in the Cockpit".  Since it is the source of power to this wire, it can be deduced the Lightswitch must have been ON at the time of failure.

PLACEHOLDER  for picture showing burned/melted insulation on Blue Wire at Footswitch and/or Lightswitch

Cynic-al Wrote:  "... I've taken the footswitch out. It seems to be lacking any form of backing that would stop the connectors shorting against the body - this can't be right, can it?

It seems that the blue wire must have shorted against the footwell, as the switch was loosely attached and moving around. I am thinking if I can secure it and put some insulation in that should sort the fault."

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1800 Wiring Diagram, marked-up in Orange to show fault current path.  Since fault was in the Lighting circuit which is considered mission critical and therefore is not fused, a high fault current enough to superheat conductor of Blue Wire (18ga), was allowed to flow, resulting in melted insulation, and "Smoke in the Cockpit" .

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As a reference, here is the underside of a used Lucas Footswitch procured once again from Chris Horn...no bottom insulator is present here either...it is also either lost, or the assembly never had one to begin with (I find this hard to believe!...if any reader has an 1800, known unchanged/unmolested since originally delivered, and can check this, I invite them to report their findings!), but without an insulator present, it is clear the terminals and their connectors would be "danger-close" to the mounting surface...a short circuit just looking to happen...and did, in Al's vehicle!  Thankfully/luckily, the resulting damage was fairly limited and root-cause was also simple to address and make right. 

 

Derek Scott of the British Volvo Owners Club and Forum, didn't like the absence of an insulated base very much either, so made one from fiber reinforced rubber...it fits perfectly, and keeps the electrical terminals of the switch safely separated and away from the conductive chassis mounting surface! 

Derek Scott picture used with his kind permission.   


Lucas Footswitch with an owner made insulator added...a very good modification when not present! 
If these were present when the switch was new must still be confirmed. 

 

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I2R Heating in the VW World:  

Not only vintage Volvo owners are plagued by I2R heating due to corroded connections!  I expect this caused some "Smoke in the Cockpit" also.

Now that my son has a VW Westfalia camper, I've been also hanging around on VW forums like thesamba.com, and VW T3 ( T25 ) Knowledge Exchange (a group), and it seems like corroded connections are nothing unusual over there either...so I'm trying to edumacate them about ACZP and convert them, one owner with corroded electrics at a time...! Here is a good example: 

A picture from Thread "Ever seen a fuse melt like this?" on VW T3 ( T25 ) Knowledge Exchange

Wayne Arthur Dunford picture used with his kind permission.


chinashit strikes again!...as another example of cheapened replacement parts, plasdick bodied fuses cannot stand the additional heat generated at the fuse-ends, which occurs with poor connections...all fuses do generate a minor and non-damaging amount of heat on their conductor as a normal mode of operation, and this raises the conductor typically just a few degrees above the ambient (as can be seen in IR scan below), but if more heat is generated, due to a poor connection, this plasdick fuse body is not up to the task, whereas a ceramic one would be!  When using these replacement fuses, it would actually be advantageous to harvest the conductive current sensing element from the plasdick bodied fuse, and replace it onto the ceramic body of a (non-china) fuse.  (Reference:  Mixing and Matching Fuse Conductors and Bodies  )  Of course the best solution is to not allow a poor connection to make excessive heat in the first place! 

Note also that the conductive element is bent into a pretzel (I expect this mangling probably occurred during-less-than-gentle removal of the fuse, which had hot-melted itself into place semi-permanently), but the element itself actually exhibits no sign of having been (over)-heated, so this is definitely not the result of over-current generated heat! 

 

My response:   [Additional Comments]

"...  When you pass current through a poor connection, it causes (excessive) heat to be generated (IR pic of an industrial fuse panel to make the point!), in this case, melting the plastic fuse body (fuse conductor is in-tact meaning that this is NOT an over-current situation! ...and melted plastic of the fusebody is clearly concentrated at the fuse-end, where the poor connections, and resulting heat-sources where located). Simple fix is to bend spring side of the fuseholder to increase fuse holding preload...also spinning replacement fuse to cut through any corrosion/contamination at the circular contact area [...yes, I recommended spinning the fuse(!), when normally I poopoo that move, but if accompanied by application of ACZP to keep the now cleaned contact area in perfect conducting condition (clean metal to clean metal under preload), it is actually a good practice, because spinning the fuse while under spring preload immediately cleans the contact area, and the encapsulation plus chemical neutralization provided by the ACZP will keep it optimum for a loooong time.   Spinning the fuse ONLY, without further maintenance is a short-lived fix which WILL fail again!]...but MOST important is to 1. Encapsulate the contact area with Anti-Corrosive Zinc Grease, because this zinc-powder filled grease is superior to the often recommended dielectric grease, because it 2. Galvanically neutralizes any corrosion which starts under the encapsulation. See: https://www.sw-em.com/anti_corrosive_paste.htm
Cheers from the vintage Volvo world, where our cars also have this style Euro-fuses, and we also hate electrical corrosion, (and rust)!"


IR scan of an industrial power distribution panel showing the effect of normal fuse heating (body of the two outside fuses), and heating due to a poor connection at the connection of the center fuse.  Actually, the left fuse top connection looks also to be making additional I2R heat, but clearly to a lesser extent than the center fuse.  Picture source: ?

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1800 (Lucas) Footswitch Evaluation: 

Lucas supplied Footswitch of the (early) 1800s [ not yet on-line]

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122 (Bosch?) Footswitch Evaluation: 

German made Footswitch of the 122s

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Links to other occurrences of "Smoke in the Cockpit", and their cause and resolution:

In this case, the Cigarette Lighter of a 122 failed in use, and since it is also not fused and the smallest gauge wire in the current path to chassis, my recommendation:  Fuse your Cigarette Lighter!

How about some "Smoke under the Hood"?   

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Reference Information: 

Chris Horn, keeper of organ donor Amazons and one of my favorite sources of used components:  agent_strangeloveAThotmailDOTcom>

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I've noted before about the manner with which Lucas automotive components (aberrations!) tend to fail...now, we have this:  


A scan from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASAís Terra satellite
...of London on the night of Al's HI/LOBeam switch "Smoke in the Cockpit" incident ...! 
Image source:  https://earthobservatory.nasa.gov/images/3200/london-england 

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External sources attributed when possible.  Otherwise this information is Copyright © 2022 Ronald Kwas.  The terms Volvo, Bosch, and Lucas are used for reference only.  I have no affiliation with the former two, other than to try to keep their fine vintage products working for me, and to help other enthusiasts to do the same, and to give the later all the grief they have earned and deserve!  (See:  Proving Everything Bad you Ever Heard About Lucas  ) The results and information presented here are my own experience, and highly opinionated impressions, and can be used or ridiculed and laughed at, or worshipped, as you see fit.  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 donít, youíre 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, or analogy (see:  ABS!) and probably wise-a** comment. 

 

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