'91 100q Alternator Belt Screech & 400-500rpm Idle Speed

[Huw Powell]

The AC turns on the hurricane fan, big electrical load.

See how that works?

On 9/19/2012 9:21 PM, mboucher70 hotmail.com wrote:
> Along similar lines, I started experiencing a belt screech earlier this
> summer.  I figured it was the A/C belt because it only happened when the
> A/C was running at the moment when the car went from stopped and
> accelerated to move off.
>
> Got all ready to tighten the A/C belt, got on the garage floor where I
> could get to it, and to my surprise, the A/C belt was quite tight.  The
> alternator belt was a little slacker than it should've been, so I
> tightened it up and the noise went away.
>
> Fast forward through a long, hot summer of hard driving and pushing this
> old beast through some record setting temperature days.  Towards the end
> of the summer it started squealing again.  But only when the A/C is on!
>
> Ever heard of an alternator belt that squeals ONLY when the A/C
> compressor is running?
>
> Belts look good, have about 10,000 miles on them, and were sold &
> installed by a shop that only does Audi/VW's, so I'm pretty sure they're
> the correct belts.
>
> -----Original Message----- From: Fred Munro
> Sent: Tuesday, September 18, 2012 8:24 AM
> To: wadd-wadd at usa.net ; quattro at audifans.com
> Subject: RE: '91 100q Alternator Belt Screech & 400-500rpm Idle Speed
>
> There are a few things to check.
> Are you using a metric V-belt (i.e from the Audi dealer) or a SAE belt from
> your local FLAPS? Metric V-belts use a different numbering system than SAE
> V-belts and some metric cross-sections cannot be matched with SAE belts.
> There are cross-references available to match up belts, but before using a
> SAE belt you should check for differences in length, cross-section, and
> ride-out. I had a squealing problem with my first Audi ( an '86 5000tq) and
> solved it by using metric belts from the dealer.
> If a V-belt is worn, it can get narrow enough that it bottoms out in the
> pulleys - if the top of the belt sits below the outer edge of the
> alternator
> pulley it may be worn too much.
> Check for wear on the pulleys. Pulleys don't last forever and these cars
> are
> getting enough hours on them that the pulleys may be losing their
> profile to
> wear.
> Are all the pulleys aligned in the same plane? If one pulley is cocked
> at an
> angle (i.e. the alternator mounts allow it to twist a bit) the belt will
> squeal and wear.
>
> HTH
>
> Fred Munro
> '97 S6
>
> -----Original Message-----
> From: quattro-bounces at audifans.com [mailto:quattro-bounces at audifans.com] On
> Behalf Of wadd-wadd at usa.net
> Sent: Monday, September 17, 2012 9:37 PM
> To: quattro at audifans.com
> Subject: '91 100q Alternator Belt Screech & 400-500rpm Idle Speed
>
> Two issues with my '91 100q
>
> -the alternator belt lets out an embrassing screech every other day
> regardless of how much I tighten it. Any way to address this? Any special
> belt or dressing?
> -the idle speed is about 400-500rpm. The car doesnt stall though.
>
> Thanks!
>
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