90q instrument illumination- Please Help!

Huw Powell human747 at attbi.com
Mon Dec 16 16:10:59 EST 2002

> Thanks Huw.  I did check the rheostat on the cluster- I'm not sure what the
> resistance range should be, but it did move gradually from very low
> resistance to around 25 ohms, so I concluded that it was ok.

Sounds about right, that is the value of the rheostat in the earlier
cars, at least.

> I am definately getting goofy results- _some_ of the dash lights are on,
> like the lights in the fog light switches, ABS switch, etc, but the climate
> control head lights go out when I turn on the headlights!  Muy confusio.

You might have issues with your headlight switch as well.  Is the dimmer
supposed to affect the cc head lighting as well or does it run directly
off the parking light circuit?  I have "manual" heating, so don't know

> I did take a look at some of the interior lighting schematic, and I was
> looking pretty closely at the "instrument panel light booster".  If that was
> fried, it looks like the cluster lighting would be out too, since on the
> schematic terminal 1 of the booster unit goes "to Console Guage Lights via
> K1".  My question- where is this module?

Dave Hord wrote:

> It's been a while since I've had a normal dash in my 90q...and had everything
> where it was supposed to be.  But I think I remember quite clearly where the
> booster is.
> Attached to the wiring harness of the three auxilary gauges is the booster. As
> I recal, the booster (looks like a relay) sits in a little clip that's mounted
> to the inside of your center console.  You will have to take the center console
> to get to it.

That is where my Bentley shows it as being located.

> http://www.humanspeakers.com/audi/cluster-T89.htm

Huw Powell



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