alternator issues

urq urq at
Sun Apr 5 19:18:27 PDT 2009

... definitely interesting ... it sounds like the alternator was not working
at first, and then it started working ... at least some.  What do you know
about this alternator, has it been in the car a long time?  If so, I'd
suspect the brushes are worn out.  The other thing that comes up every once
in a while is that the exciter circuit isn't getting power, or is
intermittent.  Check the wiring on your car to see what it is connected to
... usually it's the alternator warning light ... but that isn't always the
case.  When the ignition is on there should be 12v applied to the exciter
... you may want to check this with your voltmeter before taking the
alternator out or apart.  

On your post about the ammeter in the DVM ... it does sound like you had
moved the test leads to the location for measuring current (that would have
been my suspicion) so it sounds like the ammeter part of your DVM isn't
working, and as others have noted it may be a fuse.  While you had the meter
in the circuit were you able to see any of the things like the clock
running?  If not it will confirm that the ammeter is not closing the
circuit.  Another test you can do is to connect a 12V light across the
battery terminals to make sure it illuminates ... then try the same thing
with the ammeter in the circuit ... if the light comes on then see if the
DVM gives a reading ... 

Steve B
San Jose, CA (USA)

-----Original Message-----

I started up my '91 200 20V after it had been sitting for a few weeks.
The battery light was on, and the volt meter showed <12V (11.5?). I
checked the alternator belt, and it was in place and turning the
alternator. So I drove it for about 100 yds when the alternator belt
started squealing, at which point the voltmeter moved to about 12.5V.

Is this an alternator problem, voltage regulator, cable splice,
or something else?

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