Re: '90 Coupe Quattro stereo

[Phil@sievers.demon.co.uk (Phil Payne)]

In message <941214062403_76030.63_HHB22-1@CompuServe.COM> "Timothy P. Gallagher" writes:
> Regarding the engine noise through my 1990 Audi Coupe Quattro (31K miles
> black/black) factory-installed AM/FM/cassette stereo, it is an intrusive whine;

If the amplitude varies with engine revs, check the alternator. Some models 
have earthing straps direct from the alternator to chassis ground (like my ur-
quattro) and some don't (like my 80CD).  There should also be a suppression 
capacitor on or near the regulator.
 
If the amplitude is relatively constant but the frequency changes with 
engine revs, check that the lead to the rev counter is well away from the 
readio power lead.  The wiring loom behind the instruments may have been 
disturbed or one of the cable ties cut.

> My NEW audio electric specialist has an Audi and very much appreciates and
> understands my car.

Where is he?  Get him in here!  We Audi owners can use ALL the electricians we 
can get - and then some.

> We met and he said he NEVER uses filters because you will never get the sound
> quality you desire.

As I suggested.  It's amazing how obtrusive it can be - you will ALWAYS hear it.

> His initial reaction is it may be frayed wiring (which we observed)
> after he pulled out the radio unit.

A number of us have observed here that Audi is sometimes a bit minimalist in 
the electrical department.  31k is a bit early to have wiring harness fatigue, 
but you never know.  Check the brown cables (Audi standard colour for a chassis 
ground wire) and straps around the engine - they "work" with engine movement as 
you're driving.  If you're confident enough, start the engine and turn the 
radio on full volume, then move around the engine bay with an insulated earth 
strap connecting large lumps of metal together (engine block to alternator, 
etc.) whilst listening to the radio noise.  Sometimes you'll just hit the spot. 


Phil Payne
Sievers Consulting UK
Vice Chair, UK Computer Measurement Group
+44 385 302803 Fido 2:2503/415  CIS 100012,1660