[DML] Re: alternator troubles

[Mike Substelny <msubstel@xxxx>]

DMC Joe said:

> If the battery is week the alternator will increase the output
> voltage. When the alternator sees no voltage from the
> battery (battery disconnected) it will run "full bore", this can
> cause serious and or permanent damage to the alternator and
> or other electronic components. If you have an auto trans this
> over voltage can damage the computer governor.

My expertise is miniscule compared to DMC Joe's, but I think the
situation is even worse than he describes. As I understand it, the
alternator does not put out nice, smooth DC current. It puts out a DC
wave pattern, and the car's electronics were designed with the
assumption that a battery would always be in the circuit to smooth out
that wave.

This should not harm motors (e.g. fuel pump), relays, or light bulbs, so
disconnecting that battery might have been a good diagnostic for cars in
the 60s. But if I am right, this test could seriously damage any solid
state components in the car, including the computer, the radio, any
'Zilla parts, etc.. If I am wrong someone please correct me.

I am pretty confident that running a DeLorean with the battery
disconnected is a BAD idea!

Donald, your messages have not mentioned the reading of your voltmeter
during this adventure. If your alternator is not working at all, then
"gunning the engine" as you described last Wednesday should not have
worked. Consider the possibility that you might have a more subtle
problem. Perhaps a bad ground wire somewhere is gobbling up just enough
current that your battery must discharge to keep the engine running any
time you are at low RPMs.

- Mike Substelny