924Board.org

[dvalmont136]

I just purchased my 2nd 1980 931. Beaut of a bod and interior but hasn't run in 1.5 yrs with "ignition problems".

Upon further/first inspection today it would appear that the wiring harness from ignition burnt up, multiple wires fused together. Whatever the harness plugs in right next to that one (anyone?) also blackened, possibley burned.
It doesn't look like the damage goes all the way to the firewall but not 100% sure just yet. Cut off alot of the wrapping and it seemed like it was primarily just those two harnesses with minimal collateral damage to other wiring.

Anyone here have experience with this kind of dmg/repair? Any idea what could have caused it? Is it a difficult/expensive thing to troubleshoot and repair?

Thanks, any info would be awesome!

[ideola]

Yes, I have experience. The easiest way to repair is to find a similar enough donor car to surgically extract from and graft into your patient.

Based on what you described, I suspect it has to do with the current path in the steering wheel itself, which is used for the horn. I had an issue on my 81 NA where the turn signal was somehow shorting on that path and it cooked a good portion of the wiring harness in the steering column. Does the car have stock or aftermarket steering wheel? Those can sometimes exacerbate the problem due to improper geometry within the steering wheel hub that can also cause shorts. Not the cause in my case, but I've seen at least one post here where it was, and I believe the solution (after fixing the wires) was to do some grinding on the offending geometry.

Can be repaired by grafting as described with careful, cautious removal and splicing. Have a sharpie and lots of masking tape so you can label stuff as you go. Unfortunately, both of the spare wiring harnesses I have are currently sale pending, but if anything changes, I'll let you know. For your car, a '79 or '80 donor car would be ideal (NA or Turbo should work), although other years may work as well. Check Craigslist for parts cars. You might also check with PwrGTOGuy or Rasta Monsta, who are both parting 1980 931s. One of them might be able to extract the entire under dash harness for you.
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erstwhile owner of just about every 924 variant ever made

[john h]

Another thing that can cause the same problem is the headlight circuit could have had a fault in it, this can also cause the wiring to fry itself
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Remember a Porsche is not just for Christmas,

if you take it to pieces slowly it can provide anguish all year long!

[ideola]

True that! Be sure to check the plug at the headlight switch for signs of overheating...it won't be hard to feel, smell, or see.
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erstwhile owner of just about every 924 variant ever made

[tuurbo]

[dvalmont136]

Thanks for all the good info. Next volley of questions...

If I can isolate this to sections of 20 or so wires is it safe to assume if I cut out the bad and splice in new wires I may be good to go w/o replacing entire wiring harness?
I assume I should check all my fuses (make sure correct amps, etc) and check for burnt relays.
In theory shouldn't some fuse pop before damage like this happens?

[ideola]

Yes, you can just replace the damaged sections. I did this on my 81 NA by grafting in portions of another harness I acquired off of eBay.
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erstwhile owner of just about every 924 variant ever made