Re: Audi 100Q - Voltage on startup

[VE3LC@hydra.carleton.ca (Norm Rashleigh)]

>When I start my 1990 100Q (79K miles) the voltmeter reads about 10.5 -
>11 volts. It will stay at that reading until the engine RPMs reach
>about 2300-2500. It has only been doing this for about the past two or
>three months. Once the RPMs hit 2300, then the voltmeter will read
>13 - 14 volts.
>
>Is this normal? Or a harbinger of bad things to come?
>
>I had a similar problem with my 1988 Jetta. When I started the car, the
>battery LED would stay on until the RPMs hit about 1700, then the LED 
>would go out. The dealer said this was "normal" on the Jettas and Golfs
>and I shouldn't worry about it.
>
>TIA
>
>Mark
>'88 5000CSTQ
>'90 100Q
>'93 Passat GLX

I got an 86 Coupe GT...  No similar problem like that car, but had a similar
problem with a 75 SAAB I used to drive.  Lived with the problem for a few
years until I had to rev the engine more and more before the alternator
would "kick in".  Once it "kicked in", would seem function normally..
Well...  It finally wouldn't "kick in" at all.  I went into it to see what
the failure mode was.  I discovered that replacing the "small" ( 1 amp or
so) diodes that excite the field, the alternator was restored.  I used
"1N4007" devices that I had in my electonics parts junk box.  The alternator
would again work and "kick in" at an idle.  I suspect that through corrosion
on fatique, one of these devices failed and the alternator kind of worked
with the remaining two, (or maybe one).  Failure of one or more of the high
current stack of diodes can also happen, this usually reduces the output
capacity of the alternator but shouldn't effect the "kick in" speed where
the alternator "excites".

Well my theory anyway...

Cheers... Norm Rashleigh
          Ottawa CANADA ...  86 Audi Coupe GT  and (68 BMW R69S motorcycle).