Re: Weak Alternator?

[ti@amb.org (Ti Kan)]

Wolff writes:
> My '84 4k runs at about 14 volts indicated on the center console
> voltmeter until electrical items are switched on. Each item switched on
> (lights, ventilation fan, wipers) draws the voltage down a little until
> it is slightly below 12 volts. This is rpm independant. I changed the
> brush housing and the symptoms stayed the same. Isn't the regulator in
> the brush housing? Is the alternator bad/weak? Maybe there is something
> else that would cause this? 

The voltage dropped to that level "as seen by the voltmeter" at that
point of the electrical system because of the various losses at
connectors, switches, wires, etc.  In these older Audis, some are
probably due to an insufficient gauge of wiring from the battery to
the fuse box, from the fuse box to other circuits, as well as the
ground return to the body.  Also, as the car gets older, the electrical
contacts may become oxidized, increasing their resistance.  These all
contribute to the voltage drop.  Thanks to ohms law, given some resistance,
the higher the current draw, the higher the voltage drop.

However, I'll bet that if you take a digital voltmeter and measure you
voltage directly at the battery, it will still be up in the 13+ volts
range with all accessories running.

-Ti
96 A4 2.8 quattro
84 5000S 2.1 turbo
80 4000 2.0
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