alternator whine puzzle (X post) long

[Mark R]

First, electrical- I'd redo the primary wiring anyhow.  The stock older Audi
wire is minimal and not a ropelay construction, not is the jacket bonded to
the wire.  Add time, flexing and corrosion.. it makes sense to upgrade.
The voltage drop with the lights on is an indication of too small a wire, or
(more likely) corrosion.  Sometimes the corrosion is up inside the jacket.
Modern high quality wire will help this situation.  Upgrade the engine and
hood ground wires as well.

Alternator "whine" is typically a sound coming from the ignition harness.
Often over the radio or speakers (sometimes they don't even have to be
turned on!), but I think in your case we've decided it's a direct mechanical
ROTATIONAL noise.  I think calling it an "alternator whine" is what's
throwing people off.  A better description would be "a mechanical rotational
whine from the alternator system with direct correlation to RPMs," correct?

With the swapping you've done, it *has* to be the alignment.  What we do
with machinery is set up a laser level aligned with a pulley (rotate pulley
by hand to be assured) and aim it past the "reference" pulley to the rest.
Again, you'll have to rotate them by hand to check for mis-alignment.  If
all checks out, take measurements with a dial-indicator on the pulley.
Tighten belt and recheck.  You either have a mis-aligned system, or flex in
the brackets causing mis-alignment.  The mis-alignment could be at another
location other than the alternator, but caused by it's tension on the
system.  Some generated smoke can help with the alignment process as you'll
be able to see the light beam, and not just a dot at the other pulley.

Good luck,
Mark Rosenkrantz