[V6-12v] Weird gauge problem - 1993 90Q - Help!

Tom Christiansen tomchr at ee.washington.edu
Sat Dec 10 19:15:23 EST 2005


I'm pretty sure I've found the fuse in question on the schematic. It 
supplies the following:

Voltage regulator in instrument cluster
Seatbelt warning light
Lamp Control Module, Rear
Central Locking System
Airbag Control Module
Cruise Control
Servotronic (power steering) control module.
Fuel, temp., oil pressure gauges.

I suspect a wire has worn somewhere and is rubbing against the chassis 
or another wire. Good luck with that one...

BTW: I have no idea what this "Lamp Control Module, Rear" is. But 
apparently, the rear lights are controlled by some sort of module. Maybe 
to make it possible to run one fat power line out there and have skinny 
control wires, thereby reducing cost of the wiring harness. But that's 
just a guess. I have no idea where it might be located, but if above 
hypothesis is correct, it should be near the rear lights.


apowell at colocougs.org wrote:
> Halfway through a 300-mile round trip to eastern Colorado last night, my wife's 193 90Q developed a
> problem - I'm VERY interested in whether anybody's BTDT or knows a typical failure item that might
> relate.
> The problem is that a 15-amp fuse started blowing; when it blows, she has no gauges. No speedo,
> tach, gas, temp, etc. And just to make it more interesting, the oil pressure warning light goes on
> and off intermittently when the fuse it out. Of course, when this happened, she was 150 miles away
> and it was after dark.
> The fuse is OK as long as the car DOES NOT move, so working on the cell phone, I asked her to idle
> the car for a while and see if the oil light came on. It didn't - so I told her to drive it home.
> She got home OK with no expensive noises from the motor, so I'm confident the oil pump is working
> OK. 
> Here's the part I need to work on: as soon as she puts the car in reverse, POW! The fuse goes. I
> need to find the short and get it fixed, because it's pretty tough to find a car with no gauges and
> with warning lights going on and off. If it's driven without going into reverse, the fuse will
> eventually blow, but it takes a while.
> One possible related fact: for about six months, the power door locks have been engaging by
> themselves, usually when the car is shifted either into first or reverse. We start the car, back out
> of the driveway, and usually when we shift from reverse to 1st, we hear the door lock pump engage
> and the doors all lock. It also often locks when we close the trunk. This habit puts me in mind of
> the nasty trick that the type 44 chassis cars pulled with broken wires in the left-side of the wire
> chase on the trunk lid, but I've checked the wires and don't see anything, although I haven't really
> torn into it.
> Thoughts? BTDT's? Places to start? The problem that I need to solve immediately is the fuse blowing
> when the car goes into reverse. 
> ************************************
> Al Powell
> apowell at gocougs.wsu.edu
> 1958 Fiat 1200 Transformabile Spyder
> 1983 Datsun 280ZX Turbo
> 1993 Audi 90Q
> 1991 Camaro RS Convertible
> 1997 Chebby Blazer
> 1999 Chebby Blazer
> ************************************ 
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