Small Electrical Fire

Had myself a small electrical fire this morning, thankfully got the battery +ve terminal off before any flames started. Safe to say I was touching cloth after..

Anyway, the smoke was coming from the dash/column followed by the fuse box and on inspection the headlight switch connector looks to have started to melt and the wiring going into the fuse in the fuse box is charred, melted and thoroughly toasted.
Haven't looked beyond this yet.

I am thinking it could be the headlight switch that has failed internally, as the sides were switched on at the time and just before the smoke appeared the dash light went dim and the first sign of smoke came from the steering column.

Alternatively, is there somewhere else that could have caused the short?
Is there anything else I should be checking, other than the wires in the direct vicinity of the charred ones?
This was only 10mins into a drive too, having done longer ones recently with all lights on etc.


Things I will also be doing: Buying the fire extinguisher I keep forgetting to buy, connecting the battery isolator.

Lucky escape,Headlamp dip switch is often a problem area.This can be so if extra lamps have been fitted without a relay.Check your earths as faults here can result in the electricity trying to go where it should not.

tottot said:

Lucky escape,Headlamp dip switch is often a problem area.This can be so if extra lamps have been fitted without a relay.Check your earths as faults here can result in the electricity trying to go where it should not.

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Have got driving spots fitted but they are through a relay and on their won separate supply to headlights and connected into the main beam only (they weren't on when this happened)

Strange behaviour you say? The dashlights were flashing in sync with the hazards when I reconnected the battery, dim dip switch was off...

Pull your dash out and look for anything else that may have burned/melted some and check earth connection.If I remember right [ someone else may be able to help here] there is one behind the dash somewhere.

Have had a look, finally, at the damage and it appears to just be the sidelights line (red (well double red), its melted at the fusebox and at the switch/harness connector.

Does this double red line go direct from the switch to the fusebox or does it go via the dash illumination aswell? In other words am I going to be able to just replace the headlight switch harness connector and simply route a new double red line to the fusebox or am I looking at a full dash off and harness replacement? (switch getting replaced any way because heat damage on its connector)

also, anyone got a part number for the headlight switch harness?

as to the route cause, as only the sidelight line is damaged I'm currently going with most likely caused by a short to ground as only the side lights were on, it was only after 10 mins of being on and having been on for much longer previously without issue and the dash/DIP light changing brightness (went dim) a few seconds prior to smoke happening.

Roaming Wombat said:

Alternatively, is there somewhere else that could have caused the short?
Is there anything else I should be checking, other than the wires in the direct vicinity of the charred ones?

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I agree with tottot that the headlight stalk is often an issue, I'd suggest checking the side light wiring for a short to earth - take the bulbs out ( or the fuses if the issue is the right side of them ) and use a DMM to get a resistance measurement to earth - it should be infinite.I also agree that earth faults can cause all sorts of nonsense - and its always worth checking and maintaining earth straps as part of a service schedule... IMHO, its also worth spending some time unwrapping the loom to see if there are any shorts caused by the wires rubbing together....though this can be a royal PITA.

Roaming Wombat said:

Things I will also be doing: Buying the fire extinguisher I keep forgetting to buy, connecting the battery isolator.

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Extinguisher is always worth having..... Hindsight is a dreadful teacher.

Finally found time to look at this in more detail so I can fix it and get my wagon back on the road.
After a couple hours poking about with the multimeter it turns out the tail/side lights have been wired incorrectly when the fuse box was converted (well, half of it) by a previous owner.
Basically the right hand tails/sides were connected to the switch side of the fuse
As the fuse is intact, it would explain why the damaged cables are only on the switch side of the fuse (back up to the switch and on the harness as it comes out of the bulkhead and goes down to the chassis).

So in theory I just need to replace 3 bits of cabling and disconnect and isolate the damaged right hand tail/sides cable and its job's a good 'un.... in theory...

2 months later, found to time to look at this again and start fixing (connected the isolator up a few weeks ago)

Successfully, eventually, got the lower dash off and replaced the switch side of the RH side light wiring and wiring to the chassis harness interconnect!

Decided to investigate the state of the existing chassis harness before I replace it with a new one (to make fault finding later easier after fitting the replacement) and discovered what could be the cause of the event triggering the over current that would have blown the fuse had it been wired in correctly.

Basically, with the chassis harness disconnected (thus no rear lights connected) and the RH side lights cable connected I get both front side lights (no indicators/hazards though ). Now with the RH side lights cable disconnected I get no front side lights... I'd say its looking likely the front side lights have been daisy chained off the RH side light circuit.

Did some testing with the chassis harness connected up too, turned the side lights on and the the LH indicators came on (constant) too.. so that's a pretty firm indication there's a short in the chassis harness (i.e. something melted) as it only does it with the chassis harness connected with the side lights on (if it does it with the harness replaced then going to be fun to working that one out).

Methodical approach will sort it - post photos of the gore aswell!

Easily done, I recall wiring in a tracker and I dropped one of the wires and it hit the body, what I can only describe as a mission impossible style fuse started, I managed to move it off but was amazed how quickly it just started to melt.