Robert Coats

My '91 C4 started up just fine today, but none of the instruments on the dash are working. About 7-10 seconds after engine start, the battery warning light lit up steady. Car is otherwise fine. Drove to the office, then drove again 30 minutes later. No other symptons or problems, just dead dials.

Turn signals, headlights, instrument lights, radio, wipers, windows, and clock all work normally. Fuel, Oil Temp, Oil Pressure, Tach and Speedometer are not working at all.

I guess I should start with checking a fuse or two, but if they are okay, what should I check next?

jimq

loose or corroded contacts on the back of the instruments?

Colin 90 C2

Check out the common ground point located on the "instrument longitudinal support left".
From the diagram it looks to be about outside mirror height under the left side dash.
Sounds like the ground wire may be disconnected.
Keep us posted.

Robert Coats

What's odd is only the needles seem to be dead (except the clock) as if the car were switched off. You know when your 964 is switched off, and all the needles drop down to zero?

All the other parts of the insturments (warning lights, turn signal indicator arrows, etc.) and the rest of the dash electrics are working fine.

If one contact on an instrument were corroded or loose, I'd guess only that instrument would be dead. It seems unlikely all five instruments would suddenly loose contact independently at the exact same time.

robmug

Unless they share the same earth of course...

Robert Coats

Update:

Checked the fuse (#18, "Instruments, Diagnostic Plug" 7.5 amps) and it was blown. Tried a new fuse, tuned the key on, and all everything worked...for about 3 seconds, then, died again.

Checked #18 fuse and and it had blown again.

Okay, now what?

The only other clue I have is the day before the first fuse blew, I drove the car in a lot of stop and go traffic. Oil temp never got past 9:00 o'clock position, but lots of shifting, stopping, etc.

All thoughts, suggestions and dirty jokes are welcome

racergreg

Sounds like you have a hot wire with worn covering, so that it shorts to ground. You'll have to get under the dash and inspect the wires - look especially for any that pass by an edge of metal.

Robert Coats

Update #2:

I tried looking around the car for a short, but found nothing. Gee, there sure are a LOT of wires on this car <sigh>.

Tonight, I was out in the garage, and heard a faint ticking sound from the car. Sounded like a replay opening and closing, and it seemed to be from inside from the console, near the shift lever as near as I can tell. The battery is nearly flat, but disconnecting it stopped the ticking sound. Of course, I have no idea of the discharged battery and ticking noise are related to the #18 fuse blowing, but may be.

At this point, I feel like giving up. I'm clueless as to where to even start trying to find the problem.

It's exactly problems like this that make me want to sell the car sometimes, just as when it is running good, I can't imagine ever letting it go.

I think if I can get the car jump-started and running, I have little choice but to take it directly to a professional and hope for the best.

Eric Kessel

Can you listen to see if the clicking is under the passenger seat? I think the alarm control has a relay or two under there...... maybe you have some water under the seats?

Colin 90 C2

Robert send me a PM with your email and I will send you the wiring diagrams.
I tried to post them but I can't figure it out.

Francisco Martinez

I know this is a very old post but this exact thing just happened to me? What was your particular solution I you are still around.

Robert Coats

Whew, it's been too long now for me to recall the exact solution was on this issue. I do recall some (other) weird electrical problems due to a bad clock. The clock contains a number of warning lamps and circuits, and I ended up replacing the clock with a used one.

Good luck!

-Robert
Atlanta

bo11

Dear All,
I also have exactly the same issue.
Any fix?

It happend after i try to open my roof top and it suddently stop half way.
I noticed afterward all instruments are dead, but the car running ok.

fuse 18 was blown. I replace. Still no instrument are working.

Thanks for your help.