s-carsgo

Hi everyone,

I am trying to help my father with an interior lighting issue on his 1991 911 C2.

Last fall just before being put away for winter storage he was driving it and his instrument cluster backlighting went out. He thought it was related to the rheostat so he ordered one and installed it. No such luck.

The car went into storage over the winter and recently came out and is in the shop for the 60k service. Everything is done now except for the dash light issue which we can't seem to figure out. I ordered and installed a brightness control module (relay... 964 618 103 00) thinking it was the next logical step. Again, no dice.

My mechanic friend called to say that he believes there may be a short to ground in the wire(s) leading to the cluster... I believe it is the blue and grey wire.

Has anyone else out there encountered a similar problem? If so, any advice would be greatly appreciated.


Thanks,

Darin

s-carsgo

I think I hear crickets chirping out there. ;-)

Nobody else has ever had this happen? I've been searching forums here and at Pelican Parts w/o any success. My mechanic said he'll have to start hacking into the wiring harness to find the potential short-to-ground location. Not real crazy about going down that road unless we're sure it IS the problem.

Anyone know how to test the brightness control module relay (964 618 103 00) to make sure it is working?

Darin

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'93 Audi S4 //RS2 spec (mine)
'93 Audi S4 - mild mods (father)
'94 Audi S4 -stock (mother)
'91 964 C2 (father)
'88 928 S4 (mine)
'86 XR4ti (mine)

Marc Shaw

The thread here may be of some help. Did you check fuse #36?

Marc

s-carsgo

Thank you Marc... can't believe I missed that thread during my searching on here. Yes, fuse 36 is OK. Looks like we've got to go ground hunting. Hopefully it is as painless as it was for the other guy who found it behind the ashtray.

Johnny-Cat

Hey, behind the astray, that's me.

That was a nightmare. It was a 2 fold issue. 1’st, I knew my 964 618 103 00 dash light controller was going bad because my dash lights would not dim, just stay at a constant brightness. I also tested the dimmer switch itself and found that OK. But then I had hooked my stereo dimmer wire to my ashtray light so the stereo didn’t blind me at night. After I was putting it back together I caused a short, but it did not surface until about a week later when all my dash lights went out. That’s why I was pulling my hair out, it didn’t make sense. So first I obviously thought it was the dying dash light controller, so I spent way too much $$$$ from the dealer and put it in. As you know, it fried right away. After freeking out, and getting great advice from the guy who helped me on the thread, I was able to perform the one test (I don’t have the info in front of me) but I removed the dash light controller, applied +12v to the specified terminal and noticed it was shorting out for sure. So I checked each component that lit up on that circuit, that’s when I found the smashed wire caught behind the ash tray.

In your case it just sounds like you are not getting power to the circuit since you aren’t blowing the fuse or the controller (so you think) I would perform the first test of removing the controller, find out which wire is +12v, jump it to the wire that goes out to the dash lights. If you blow your #36 (I believe it is) you know that something is shorted out. if that is not the case, it will be one of the following: Head Light switch, dash light dimmer switch, or the controller.

Good luck! If you lived in AZ, I would help you out!

s-carsgo

Thanks for the assistance guys. So here is the follow up story on this whole fiasco. My mechanic started tracing the wire to each component looking for the trouble spot. Everything came back as being OK. He started plugging things back in and low and behold the interior lights are working now as is the dimmer. Problem solved? Well, not quite....

So now the interior lights work aside from the headlight switch BUT the airbag, abs, and rear wing (?) lights are illuminated. My mechanic/friend noted that he did run the battery down during his diagnostic testing and thought perhaps the voltage drop tripped the lights. The thing is, I am sure we've run the battery down dead as a doornail in the past while in storage over the winter and never had any airbag or other lights upon installing a new battery.

The other bummer is that the mechanic doesn't have the tools to reset the airbag warning lights... that may require a 2 hr drive to either Des Moines or Minneapolis.

Anyone ever seen this sort of thing happen or is our 964 just an Octoberfest special perhaps? ;-)

jimq

There is a loaner scantool setup that will reset all the lights. Its somewhere in NC now. Maybe the person that has it will chime in.

foxford

try
http://www.porsche964.co.uk/technical/clock.htm

The airbag/seatbelt/master warning light gremlin may be in play here.

I have a Bosch "hammer" in the western suburbs of Chicago.
If you can get it here, I can null the system's faults.

Good Luck!