Electrical smell and then smoke!

Evening everyone.

Had a bit of a drama today. Heading out to the shops after walking with the dog and we smelt a strong electrical smell, after wondering who it was we then saw smoked and grabbed for the isolator.

After a few quick checks on the side of the road I found the sidelight wire from the headlamp switch burnt out so we were able to limp home. Stripped the dash apart for access and found the wire (red on pic) for the sidelights burnt out all the way to the fuseboard and also the wire to the dash lighting on/off burnt out from the switch. Strange. Spent the afternoon replacing these.

My question is..... Having checked the switch I do not have any power coming out of the red wire on sidelight setting but it does send power to this wire and blue when on full headlights. Basically I have no lights on sidelight setting but do have sidelights and dipped beam on the dipped beam setting.... My guess is the switch has gone faulty?

Dash back together and inside for dinner now.

The headlamps are fed directly through the switch. ie the switch doesn't operate a relay which then carries the full current. The full current for the headlights goes through the switch. As the vehicle ages the circuit degrades and resistance increases. Heat generated causes the switches to break down. They are prone to it. I had to replace mine years ago. I've since fitted a boomslang harness so the headlights are now powered, via a suitable relay, directly from the battery. Helps with brighter headlights too.

Al2O3 said:

The headlamps are fed directly through the switch. ie the switch doesn't operate a relay which then carries the full current. The full current for the headlights goes through the switch. As the vehicle ages the circuit degrades and resistance increases. Heat generated causes the switches to break down. They are prone to it. I had to replace mine years ago. I've since fitted a boomslang harness so the headlights are now powered, via a suitable relay, directly from the battery. Helps with brighter headlights too.

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Thanks AI203, looks like a replacement switch for now then, i have the MOT this month so will get her through that first.

Replacement switch fitted and has solved the problem, £17.00 + VAT for a Lucas switch

I would be concerned the fuse did not blow feeding the side light before the wire melted that is if it the correct size fuse has been fitted the head light mod would not reduce the current drawn by the side lights which is small compared to head light
but would reduce the head light current through the switch ,

mystery said:

I would be concerned the fuse did not blow feeding the side light before the wire melted that is if it the correct size fuse has been fitted the head light mod would not reduce the current drawn by the side lights which is small compared to head light
but would reduce the head light current through the switch ,

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Yes that was my thought too, both fuses did not blow, one had a 5 amp and the other had the correct 2.5amp fuse. We acted very quickly using the emergency isolator so maybe this stopped it blowing, not that knowledgeable about electrics yet, maybe it should have popped quite quickly.

The wire that melted what section pics always helpful ,the switch was probably destroyed by the current passing through it I assume it has the 20 way blade type fuse box 1986 ,I would also be wary of cheap fake fuses and would only buy from known
source,the current drawn to melt the cable should have blown the fuse way before the cable reached melting point you should check the other cable grouped around the melted one for insulation damage especially where they pas through the bulkhead and where they are grouped around the headers for peace of mind