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

[Joshua Van Tol]

Another possibility that hasn't been mentioned is that the harmonic
balancer is de-laminating. I.e. allowing the inner part to turn with
respect to the outer part. This could make some noise, and would only
happen when the total load was high. But that's unlikely.

Josh

On Wed, Sep 19, 2012 at 10:05 PM, mboucher70 hotmail.com <
mboucher70 at hotmail.com> wrote:

> Thanks Huw,
> I totally see how that works :-)
> In fact it was my first guess.  But I also thought about the other
> suggestion, that the effort to turn the aging A/C compressor together with
> worn pulleys was causing the flywheel to be pulled towards the alternator.
> I wasn't sure which was the more likely cause.
>
> -----Original Message----- From: Huw Powell
> Sent: Wednesday, September 19, 2012 9:42 PM
> To: quattro at audifans.com
> Subject: Re: '91 100q Alternator Belt Screech & 400-500rpm Idle Speed
>
>
> 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@**audifans.com<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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