Replumbing 12V to the Instrument Cluster

My '79 928 suffered from a very dim back light, volt meter reading low (would go down to the red at idle with lights on) and the temperature gauge was reading too high (about 20% hotter than it should be).

I confirmed that the alternator output is proper with a volt meter and that the engine temperature was normal using a heat sensor gun.

I mentioned this to my shop, Exotic Motorwerks. Super mechanic Dan figured out a way to pull 12V directly from the Central Electric, used a relay to control switching, and I now have the full 12V to the instrument cluster.

The Voltage and temperature gauges are now showing true values and the back light is bright.

He also wired it such that I can switch back to the original "low voltage" circuit that Porsche used.

It is surprising how much better you feel when the gauges are where they should be. I knew that nothing was wrong ... but always staring at the wrong values was a downer.

Rich
'93 GTS cover girl
'87 S4
'79 5-speed
'79 Euro track beast

Rich,
That is very interesting and I have a similar issue on one of my 82 cars.
Any chance of more details for those of us who are electrically challenged?
Best,
Roger

Roger Tyson;13784 wrote: Rich,
That is very interesting and I have a similar issue on one of my 82 cars.
Any chance of more details for those of us who are electrically challenged?
Best,
Roger

Or for a better term electoral difficulty

Roger Tyson;13784 wrote: Rich,
That is very interesting and I have a similar issue on one of my 82 cars.
Any chance of more details for those of us who are electrically challenged?
Best,
Roger

I'll see if my mechanic is willing to part with his trade secrets ... or provide some hints.

My '87 S4 also suffers from low battery voltage display - it seems that most 928s have the problem. Where and why the voltage drop, I don't know.

Rich

my car showed a low voltage when i bought it last may. perhaps you have all done this but i was still going over things little by little then.

i took it to a radio shop to change the head unit etc and they did notice voltage in general was kinda low. a simple cleanup of the ground point in the rear brought the voltage all around up quite a bit and also allowed the head unit to play up to snuff.

still i do have some other electrical issues...

That is the most common cause of low voltage in a 928... dirty ground points and there are something like 13 of them in an S4!!! YOWZA!!! Find them all and clean them up and you will be MUCH better electrical power in a 928!