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Car won't turn off!! Burnt ignition switch wiring. WTF?

Posted: Mon Oct 14, 2013 9:13 pm
by jules
Well, that was fun. Got home, switched off the car and it still runs!

Upon pulling the ignition switch wiring I find the below. Looks like the lugs have melted the plastic plug and are shorting.

Is this just an age thing, or has someone else experienced this? If so, any idea on the best way to go about replacing the plug?

Thanks

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Re: Car won't turn off!! Burnt ignition switch wiring. WTF?

Posted: Mon Oct 14, 2013 10:03 pm
by davekmoore
Pure guesswork here but:

It looks like you have an NA, so at least 16 years old. Electrical stuff can go wrong at that age in any car. Thank your lucky stars you don't have a 16 year old French car - or a 3 year old one for that matter.

It's odd that those connections are that badly affected. Shouldn't a fuse or a relay have tripped out before that happens?

Re: Car won't turn off!! Burnt ignition switch wiring. WTF?

Posted: Mon Oct 14, 2013 10:51 pm
by jules
From memory the fuse for that circuit is a big one!

Re: Car won't turn off!! Burnt ignition switch wiring. WTF?

Posted: Tue Oct 15, 2013 8:58 am
by jules
The symptom was pretty odd. The car would keep running with the key out. The ignition lights were illuminated on the dash, however all accessories were switched off. Sounds like the 12v constant feed to the IGN lead were touching...just.

For now I have it plugged back in with the shrouds off and the car is working as normal. I have not done any electrical work on the car in this area.

I am hoping that perhaps being an "old girl" ('91 Malibu), that this is just a case of resistance built up over time.

I'll need to investigate repair options (maybe I can get a loom from a wreck), but was interested in whether you guys think this could be in any way age related, or whether I should get out a multimeter and start testing?


Cheers
Jules

Re: Car won't turn off!! Burnt ignition switch wiring. WTF?

Posted: Tue Oct 15, 2013 9:48 am
by emily_mx5
Do you have an alarm/immobiliser fitted? They always cause electrical problems, I would take it out.

The copper contacts in the ignition barrel get worn out and corroded, there is a god article on miata.net about cleaning it.

The loom is part of the car harness, doesn't unplug. You would have to cut the old plug off and solder/crimp in a new one.
You could probably find a new plug online somewhere that sells automotive connections, maybe even Narva make one.


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Re: Car won't turn off!! Burnt ignition switch wiring. WTF?

Posted: Thu Oct 24, 2013 3:17 pm
by jules
Big thanks to Eric and MX5 Plus!

a: 1x Narva 6 pin terminal block with lugs (also available from Supercheap)
b: 1x Slightly used ignition switch
c: 1x Precision skilled soldering job from yours truly ;-)
=
d: Factory perfect result!

Ta Da!
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