90q instrument illumination- Please Help!

DePenning, Charles [FRCO/MTN] Charles.DePenning at EmersonProcess.com
Mon Dec 16 09:30:06 EST 2002

Thanks Mike.  The wire that I left dangling was a gray/blue wire that I
believe is the 'standard' color for dash illumination.  I _think_ the whole
problem began when it grounded out on something- the back of the radio, the
climate control head, something like that.  I will check the grounds on the
back of all of the switches in the general vicinity, because I did do some
tugging to get the white antenna lead to the radio.  I think the circuit is
ok though because the license plate lights and glove compartment lights
still work.  Just no dash lights!  Argh.

Does anyone out there have access to the schematics for an '89 90q (circuit
for fuse 14) that they could copy for me?  Or, better yet, sell me a set?  I
think I need to trace the circuit to get to the bottom of this.


Charley DePenning
Ames, Iowa
'90 CQ; '89 90q; '84 4kq; '83 5kT and counting.....

-----Original Message-----
From: Mike Robinson [mailto:quattrofan at sbcglobal.net]
Sent: Sunday, December 15, 2002 11:58 PM
To: DePenning, Charles [FRCO/MTN]; 'quattro at audifans.com'
Subject: Re: 90q instrument illumination- Please Help!


I have taken out the entire front dash on my 88 90q a few times.  I have run
into this problem before, but because it is an electrical wiring issue, the
culprit could be anywhere.  First things first, what was the dangling wire
originally connected too?  I assume it could be a ground.  When Hans and
Dieter designed the dash wiring on the 90q's they daisy chained a lot of the
grounds together.  I had accidentally removed a small brown ground wire
which went from the rear defroster switch to somewhere else (can't remember
if it grounded out at that point).  My switch was bad and I figured I didn't
need the wire there.  Turns out this little wire was part of a daisy chain
which grounded the entire fuse 14 circuit in the dash.  If you look at the
back of the rear defroster switch it has two brown wires, one is the ground
coming in from the instrument cluster and the other is the ground going out
for the switch (they are basically connected at the same port).  This is
just my own personal experience, it really could be any wire.  Check to make
sure all your grounds are complete (usually brown or black wires).

That¹s all I could really think of. I hope it helps you out somewhat.

-Mike Robinson
1988 Audi 90 quattro SS
243,000+ miles

On 12/15/02 7:38 PM, "DePenning, Charles [FRCO/MTN]"
<Charles.DePenning at EmersonProcess.com> wrote:

> Hi all- it's been awhile since I've posted.  Hopefully someone out there
> had experience with this and can help me!  I've got an '89 90q that I
> recently bought and put a new radio in.  During the installation, I
> accidently left an illumination wire dangling uncovered.  It must have
> grounded on the top of the climate control box because my dash lights (and
> license plate lights, glove compartment lights i.e. fuse 14) were out.
> Blown fuse.  I kept blowing fuses trying to track the problem down.  Once
> finally found the likely cause (the dangling wire) I put a new fuse in,
> while it did not blow when I turned on the lights, I still have no dash
> lights.  So now what I am worried about is that I damaged something in the
> circuit during this repeated testing phase.
> What I have checked:
> -Circuit for fuse 14 is good, other than dash lights (license plate lights
> and glow box lights ok)
> -Turn on parking light switch on stalk, no lights (even clock goes dark)
> with exception of computer, which does dim with pot on cluster.  No
> control lights either.
> -no voltage to the 'dangling wire' with stalk switch on, regardless of pot
> position
> -removed cluster.  Checked resistance of pot- ok.  Checked voltage supply
> pin 1 of yellow connector (per Bentley)- ok.  Checked voltage regulator
> Bentley- ok.  Looked at soldered connections on cluster where
> multi-connectors go- look ok, but hard to verify.
> So now I have the cluster out and in pieces on the bench.  Are there other
> things to check before I reassemble?  What about other voltages on the
> multi-connectors?  I'm worried that I popped a trace on the board or ???
> I have part 1 of the Bentley for this car, but no wiring diagrams, so I am
> (ha ha) somewhat in the dark on the circuit.
> I sure would love some assistance on this, since it is my commuting
> and I am hesitant to reassemble for tomorrow before knowing I have done
> everything I can while the cluster is out.
> Thanks much,
> Charley DePenning
> Ames, Iowa
> '90 CQ; '89 90q; '84 4kq; '83 5kT and counting.....

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