A Ghost in the Electrics

[Zippy]

Hi fellow 993ers

Having odd electrical blips on my 1996 C4 Coupe where the radio and instrument cluster will go off then straight back on. This only happens when you also have the blower on and/or operate the windows and/or flash the headlights. This wouldn't worry me greatly but if it happens just before you stop it can cause the immobiliser to do bizarre things.
As soon as it happens (every 6 months or so) I go round all the earths I can get to, take them off and clean and tighten them, which cures the problem. I was wondering if anyone can identify a common earth or something else which would be a longer term fix?

Did 12k miles as a daily driver last year, including one very interesting 140 mile journey home through deep snow and blizzards where we weaved through the carnage of crashed and abandoned vehicles. The old girl lives outside in all weathers as well and I've have had no other problems at all, so I'll cut her some slack!

Cheers

 

[verysideways]

How very odd - have you checked the earth strap on the battery too?

 

[John H]

Braided earth straps can deteriorate to the point where they are passing very little current, yet still look OK. Suggest that instead of just cleaning the earth straps, you should replace them with new ones.

 

[Zippy]

Yes I've checked and cleaned the main battery earth strap and it looks fine. It seems to be one of the smaller earths under the bonnet or under the seats that fixes it. It only takes me an hour or so to go round them all, so not too bad, but I'll try doing them a few at a time and narrow it down.
From the response it looks like it's a unique feature of my car!

 

[John H]

ORIGINAL: Zippy

Yes I've checked and cleaned the main battery earth strap and it looks fine.

That's the problem though, you can't tell by looking at it. The little wires all start to snap internally, and although the strap still looks OK, it isn't conducting electricity. This was a known problem on 964's, and as 993's are getting to the same age now, I would assume it might afflict them too. Best of luck.