I have a 94' Escort with the 1.9 engine. The alternator/battery charging
light has been coming
on, but only when the engine speed reaches about 2000/rpm. It goes out
when the RPM drops below 2K. The headlights dim a little when the
warning light is on. They get brighter when the light goes out. This
would seem to indicate that the alternator is not charging above 2K-RPM.
I don't think the drive belt is slipping. There aren't any noises
The slip rings can be slightly out of round.... if the brushes stick
slightly in the holders, they can be able to follow the slip rings at low
rpms but "float" at higher rpms.
Given the age of the car, I would probably opt for a good quality rebuilt...
If finances are a concern, there is a chance of success in replacing the
brushes and cleaning carefully. Having alternator ripple tested at low rpm
may uncover failing diodes that may colour your decision. If you have a
decent DMM, you can test for ripple using the AC 2 volt scale.... Start the
engine and turn on all the accessories to load the charging system.... with
the DMM on the AC 2 volt scale, attach one probe to a good chassis ground
(not to the battery) and the other probe to the output terminal on the
alternator. Ripple voltage should be below 0.5 volts.
I forgot to mention that the alternator is not the original. I had to
replace that one about two years ago. I got a rebuilt one from
'Advance'. It's supposed to have a lifetime warranty so I'll take it
back. Thanks for all the replies.
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