lverheul

Listers,

I have a riddle for the electrically inclined here: I have a 964 from 91, which I just bought from a specialist. The car runs great; mechanically sound, great interior, but there is one/multiple annoying electrical niggles in the dash:

1. With the ignition in ACC all warning lights come on and go out when you start the car, however the master warning light always stays on. You can turn this off by pressing the reset button on the center console; it will then stay off until I start the car a again.

2.
The backlight on the LED trip computer does not work. However, when you turn on the rear wiper, the light comes on... When you turn off the rear wiper, it also goes back off. Also the rear wiper has a mind of its own on where it decides to stop.

3.
Finally, the clock and the clock backlight don't work. The control lights on the clock display all work fine.

So far what has been done to remedy, but what has had no effect: swap out central informer, swap out tacho, swap out rear wiper motor. Any suggestions on next steps? Both me and my (experienced Porsche) mech are a little bit baffled.

One thing I will try is solder all clock connections, but besides that I am a bit of a loss.

Cheers,
Liam

klr10

It sounds to me like a bad earth behind the dash somewhere. I would start by checking the power and ground connections to the clock, that sounds like a clue.

Good luck, hope you find the problem.

KaiB

Yep. Search herein for the clock gremlin.

lverheul

Played around a little with soldering iron. I managed to get rid of the master warning light and the was able to restore the clock backlight. Couldn't get the clock to work, even after soldering and applying 12v directly to the clock. In desperation :-) I ordered a used clock through eBay. Next up: soldering a new transistor into the trip computer; hope that will solve the back-lighting issue on the LCD screen

lverheul

So... together with my friendly Porsche specialist I was abel to solve the problem. There was a bad connection in the fuse box on the fuse of the rear wiper, so there was no permanent 12v going to the rear wiper.

Apparently this 12v is also linked to the backlight of the BC and the permanent 12v of the clock. After wriggling the fuse a little, everything started to work again. (of course this was after the dash and the luggage compartment had been stripped down to get to the wiring, which was not neccessary...). But hey, I'm happy!

bertever

I had the master warning light for years with no other lights. While converting the instrument lights to LED I noticed an empty hole for the CEL. inserted a bulb and had a constant CEL. Apparently the PO got tired of the red light and pulled the bulb when he converted the US spec car to a no CAT/ no O2 sensor car for use in the Middle East. I now have a working O2 sensor - no CEL, no code faults on DME. BUT, now the light stays on for the cab top open all the time and I'm back to resetting the blasted master warning light every time i start the car. :{