[urq] alternator whine puzzle (X post) long

[j.koenig]

For what it's worth, the hypothetical, electrically-produced sound I think I'm talking 
about it more of a whistle, pretty high-pitched, and not something you would confuse with 
the screech of a slipping belt.

Another thought:  a mechanical problem should vary directly with engine speed, while the 
ambiguous 'electrical whine' would more likely vary with electrical load -- lights, etc. 
(not necessarily rpm per se).

This should be a good one, once you get it figured out...


----- Original Message ----- 
From: "Brandon Rogers" <brogers at terrix.com>
Subject: RE: [urq] alternator whine puzzle (X post) long


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

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