No dash lights
 

As promised, I said I would post why I was digging into my dash.
All my dash and console lighting has gone out!
Everything was fine until I went over a bump in the road... Had the head lights on and all the dash back lighting and lower console were lit up as they should be. Hit a bump and everything went out. Hit another bump and they all came back on. It went like that for a couple days then finally every thing went out. The warning lights, over head interior light and key light all still work, just the gauge illumination and lower console lights have gone out. I have tried the obvious, fuses, but all are good. Next thought was the relay. Local Porsche dealer service manager told me, "its not the relay...in 25 years of Porsche service I have never seen that relay go out." ...ok...
My next thought was maybe a loose connection, given how they went off/on with bumps in the road, in the dash, behind the gauges...? Well, can't find anything useful in there.

Anyone have any ideas?

Thanks,
Mike

Loose connection is a good bet. When I removed my CCU, I didn't have one of the plugs inserted correctly. After a couple of days, my dash lighs went out (just like you described). I knew that was the only thing I had worked on, so I reached under my dash and moved the thick bundle of wires and my dash lights flickered. I then removed the CCU again and found the clip not holding the small plug. I reseated it and clipped it and have not had a problem since. Not sure what that plug has to do with instrumentation lights, but that worked for me.

Check your R11 relay. This is a known issue with it sticking. Also, tail lights won't work I believe (brakes do though)

Make sure your ground is clean & secure.

Thanks for the inputs.

Took out some of the gauges and poked around inside the dash. Couldn't find anything obvious. Now this may sound dumb, but where exactly is the CCD? Will have to admit the 993 is a little different from my previous 82 SC Targa...

Thanks,
Mike

Did you check the R11 Relay? That service manager knows jack. I think you can swap it out with another relay in the fuse box but forgot which one. Do a search. I wouldn't start anywhere else unless your 100% on that the relay isn't bad.

You mean the CCU (Climate Control Unit) and is between the steering column and the radio.

Ah, climate control unit...duh. I feel dumb now. But, what would the CCU have to do with dash/console/instrument lights? Just ordered a new instrument panel relay (R23, I think), a 6 pin relay, of course it's a one of a kind relay up there in the fuse box...ugh.

Why check R11? All my external lights work (rears and brake).

I don't know if this helps with the trouble shooting, but, my overhead interior light only come on in the "on" position. Does not come on in the "open door" position. Also, the little light over the ignition key is always on... Is it supposed to always be on? And when I say always, I mean always...


Mike.

I'd vote for a bad ground over a bad relay, considering your lights were on, and then flickered, then died. It's hard for an energized relay to stick and cause lights to go out.

Mike, did you determine that visually or with a DMM?

With the instruments removed, you should have checked for power and ground. You're not getting one or both of them.

Do you have the electrical schematics?

New discovery...?
 

IXLR8,

Nothing special used, just noticed as driving. The gauges were all lit up (along with center console and ccu) and suddenly it all went out. I went over a bump in the road and they came back on... And it work like that for a couple days then nothing... Playing with the light switch did nothing, the dimmer knob...nothing. Checked the fuses all good...so the first thought was the relay, followed by maybe a loose wire harness connection. I have no idea, just trying to be logical about it.

Now here is the new discovery. When the problem first started all the fuses were good. Now after playing with things, wiggling wires, relay out/relay in, switches on/off, gauges out wiggling more wires... Today I discover fuse 36 blown (license plate light and instruments). I do not recall this fuse being blown previously. So fuse replaced and "result!" I now have dash lights...! However, before I get too excited, the dimmer knob is not working and then gauges are rather dim, but working. So now, I don't know if my rooting around has caused a short and blew fuse 36, or if it was always blown and I had just somehow missed it. Maybe the relay (23 I think) is sticking and that's why the dimmer knob does not work. I have a new one coming in the mail, will test it before hopefully getting to return it ($114.00 relay!).

I know, long discussion, but no, I do not have the wiring schematics. Right now, I don't have much of anything to work from, just a pre-existing generally knowledge of how things work...kind of.

Cheers,
Mike

Again, a sticking relay should not be the culprit if your dimmer doesn't work. Most companies will NOT accept returned electrical parts.

Mike, the dimmer control connects to a "Control Unit Instrument Light" module. It is an electronic device and if shorted or drawing too much, could be the problem.

Power to that "Control Unit Instrument Light" is fed by the Light Switch which also feeds fuse 36. Fuse 36 then feeds the licence plate lights and R12 (Bridge).

I'd pull one item at a time and see which one blows the fuse. Thats the easy way to determine where the problem lies if you are not comfortable using a Digital Multimeter (DMM). BTW, a DMM can be had for under $15 at Wal-Mart. I keep this DMM in my 993's kit.

Get back to us with what you find.

Alex,

I'll take a look this afternoon.
Do you know where the "Control Unit Instrument Light" is located? Something easy to get at?

Thanks,
Mike

You may have a problem with Relay Number 24, Part No. 964 618 103 00. Read the below thread I started in March of 2011.

https://rennlist.com/forums/993-foru...ut-solved.html

Here is the thread I found that helped me solve the problem;

https://rennlist.com/forums/993-foru...his-relay.html