[urq] alternator whine puzzle (X post) long

Mon Oct 30 11:42:33 EST 2006

Guys-
Based on my tests so far - I'm starting to think this (John Koenigs
response just below) may have some merit here.  I loosened the belt
further over the weekend and it made no real difference that I could
tell.  I would think a looser belt would make the sound go away some if
it were alignment - as the stress would decrease.

So lets talk about charging.

My battery cable, which originally went straight to the alternator, with
a "branch" to the starter, is now different because the alternator is on
the other side and the battery cable will not reach.  The battery cable,
BTW, is from a 200 20V.  So now the battery cable exits the frame rail
and goes to the starter directly and a new, longer, "branch" goes over
to the alternator.  According to my gauge, I'm seeing about 12.3V at
night with lights on, about 12.9 to 13V during daytime.  Remember I've
tried 3 separate alternators and the output has been consistent too.
Any input on the charging wiring aspect that I should check? Is there a
way to add a secondary ground strap?  Is the alternator working overtime
hence the whine?  What would cause this?  Voltage Reg? Wiring? Anything?
Anyone anyone?  Bueller bueller.

Thanks again

Brandon
'84 urquattro 20Vt
'01.5 S4
'98 A4 1.8Tq

-----Original Message-----
From: urq-bounces at audifans.com [mailto:urq-bounces at audifans.com] On
Behalf Of j.koenig
Sent: Thursday, October 26, 2006 6:11 AM
To: urq at audifans.com
Subject: Re: [urq] alternator whine puzzle (X post) long

I'm no electrical engineer, and this may sound crazy, but I seem to
remember something 
from years back about alternator "whine" issues being electrical rather
than mechanical --  
something about improperly connected diodes or some such.  I'm sorry I
can't be any more 
specific, but you might try looking at mounting/connecting/grounding
issues, since they 
all do it, you have changed the game, and you can't identify any
mechanical cause. Good luck. John

----- Original Message ----- 
From: "Brandon Rogers" <brogers at terrix.com>
To: <urq at audifans.com>; <quattro at audifans.com>; <200q20v at audifans.com>
Sent: Wednesday, October 25, 2006 6:31 PM
Subject: [urq] alternator whine puzzle (X post) long

OK Guys -
here is a frustrating one - bear with me.  Subject is an '84 urquattro
with 3B 20Vt motor.  The car still has a/c, the stock urq unit which is
a mini-York mounted on the driver side.  I recently installed a larger
intercooler from a 944 turbo.  This necessitated moving the alternator
from the stock location on the urq (on the passenger side) to the driver
side.  Most people who do this ditch a/c, but as noted I did not and
don't want to.  2Bennett makes a bracket (steel I think) that mounts the
alternator to the underside of the urquattro a/c compressor, allowing
for extra room on the passenger side for a big intercooler.

So I got the bracket, got hold of the proper alternator (thanks to
another Lister who had one in his basement collecting dust).  I mounted
it up, it charged fine, but it whined.  As revs would climb the whine
would get louder - loud enough to almost drown out a 20Vt with a test
pipe and no center resonator.  At idle, no noise.  Off the car,
alternator spun like butter.  But I figured a bearing was going bad due
to the noise.  Had new bearings installed - rebuilder did call me, BTW,
to tell me the unit worked fine but I told them to replace the bearings.
Reinstalled alternator.  No real difference - still whined.  Hmmmm.
Checked belt tension but this is clearly a mechanical whine.  Verifed by
another Lister later in this process.  So I drove the car WITHOUT the
alternator. No whine.  Okay good - must be the alternator.  Reinstall
alternator without voltage regulator.  Whines like before - ok gotta be
bearings.  So I went to a local salvage yard and got another used
alternator.  Mounted it - ran the car.  Whined like the other one.  Okay
could this be coincidence - 2 alternators with bad bearings?

So I checked the alignment of the alternator to the pulley - seemed
maybe slightly off so I took a grinder to one of the holes to line it up
best I could tell.  No real difference - still whined.

So I took the car back to the place that rebuilt the alternator - had a
guy ride with me to hear the noise.  He said it didn't necessarily sound
like bad bearings, but I informed him there is no noise with no
alternator.  His rebuilder said she has seen one or two over 20+ years
make noise and need a new body.  Told me to take it off and bring back
and they would rebuild and swap bodies - and since I had two alternators
I could provide another body - problem of course being both of those
units whined - so I was still a little hesitant.

Just to experiment, in case there was some sort of harmonic resonance
occuring or something??? I then installed a rubber sheet gasket between
the contact areas of the 2Bennett alternator bracket (it is a plate with
tabs hanging down) and the stock a/c compressor bracket.  This made
virtually no difference.

As luck would have it - another lister also had an alternator I could
try.  Well it whines too!  So 3 separate alternators whine.  I did take
the car out again prior to instal of alternator #3 to make sure the
whine was gone with no alternator.  This was the case.

ACKKKKKK!!!  How could a bracket or alternator placement make 3 separate
alternators whine!?!?!?  I talked to 2Bennett today and Andrew Bennett
said he's never heard of this.  That said, Andrew Finney had one of
these on his car and he did tell me his alternator was a little louder.
At this point I've asked 2B to send me a new one and I then send this
one back - hopefully they will follow through.

But more important - any idea what the heck could be going on??????

ANY input appreciated.

Thanks for reading - I'm currently not receiving mail mail from the
"mother List" so if you reply from there please cc me - thanks!

Brandon
'84 urquattro 20Vt
'01.5 S4
'98 A4 1.8Tq

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