Re: Less HELP!!

[raf40@oes.amdahl.com (Richard Funnell)]

>>
>> This part sounds as if the alternator isn't working properly.  Alternators
>> are 3 phase devices, using 6 diodes to connect the output from 3 AC phases
>> to 1 DC output.  If 1 or 2 phases wasn't working, probably due to bad main
>> diodes, the alternator wouldn't be able to generate enough current to
>> charge things until the engine is turning faster than idle.  That may
>> explain what you're seeing.
>no,no,no.....i changed the alternator and voltage regulator already
>the dealer seemed pretty clear that if the battery light did not
>come on when the ignition switch was turned that it would not
>"excite" the alternator which causes it to charge.

The "battery" light in the dash is connected before the main diodes.  If it
doesn't come on when the key is turned on, either it isn't live at the
alternator, or the feed to the light is bad.  The light doesn't excite the
alternator, it indicates that the alternator is excited (so to speak).  If
you really don't think this is true, it would be easy to connect a separate
light to that wire from the alternator and see what happens.  You should be
able to find that wire at the alternator, and you should probably meter it
anyway.

The light has one side connected before the main diodes, and the other side
to the battery.  It comes on when the alternator side is at 0 or low
voltage, which places 12V across the light.

It's tough to say from a distance, and I'm going from memory, but I still
suspect the alternator.  The fact that you just changed it makes me more
suspicious, not less.  If the light isn't coming on, though, it may be
something other than diodes causing your problem.  I don't recall the guts
of an alternator, but the light needs some current path to ground (slip
rings and coils?).

There was a discussion some time ago about alternators that didn't start
charging until the engine was rev'd up some, although in those cases once
started it kept charging.  I'd start thinking about taking it to an
electrical specialist.

>I check all
>dash lights and traces, anything I'm possibly missing? Relays?
>I already changed the relief relay and all other relays in main
>fuse box, are there any that possibly could be bad under the dash
>board?

I'd bet dollars to doughnuts that it isn't a relay or any such obscure
component under the dash that's causing this charging problem (I know
them's fightin words with an Audi).  You need someone who understands what
each component is doing, and frankly that doesn't include most mechanics I
ever met.  It would be interesting to see the results of a load test on the
alternator, and I'd start looking for the warranty for the one you already
paid for.

Good luck.

Richard Funnell,
San Jose, California
'83 urQ
'87 560 SL