alternator problems
Thread Starter
Racer
Joined: Jul 1999
Posts: 312
Likes: 0
From: Antioch, CA USA
alternator problems
I am working on my other daily driver car and can't figure out a problem I'm having. The alternator isn't charging. Car starts but the ammeter shows no charge and if I disconnect the battery it dies. Took the alternator to Kragens and it tested ok. Where should I be looking for problems?
Instructor
Joined: Sep 2001
Posts: 171
Likes: 1
From: Rolla MO
Re: alternator problems (blackguard)
Well if the car starts then the ammeter should show a negative charge, meaning the car is running off
the battery and not the altenator. My guess is the votage regulator is bad (if separate from the altenator)
or you have a broken wire/bad connection at the back of the altenator. Take a voltage reading off the altenator
with the engine running... should be around 13 volts. That will confirm the altenator is working. If you
get 13+ volts, start looking at the connections and wiring harness(es) - there has to be an open circuit
somewhere.
Good luck,
Hank
the battery and not the altenator. My guess is the votage regulator is bad (if separate from the altenator)
or you have a broken wire/bad connection at the back of the altenator. Take a voltage reading off the altenator
with the engine running... should be around 13 volts. That will confirm the altenator is working. If you
get 13+ volts, start looking at the connections and wiring harness(es) - there has to be an open circuit
somewhere.
Good luck,
Hank
Melting Slicks
Joined: Dec 2000
Posts: 3,407
Likes: 2
From: Carmichael CA
Re: alternator problems (blackguard)
Is this "other" vehicle a FORD or GM? Does it have an internal or external regulator?
I'm not positive, but there needs to be a 12V line running from the RUN terminal of the ignition switch to the alternator Stator terminal. If there isn't 12V at the S terminal then the alternator won't put out. Also, when the alternator is putting out then the Field terminal will show a voltage somewhere between 6 (low output) and 15 (high output)...if you have 12V to the S terminal, but nothing at the other then use a wire and connect the S and F terminals together to "full field" the alternator. If that turns the alternator on, then the problem is the regulator.
Kragen is usually good at testing alternators, so check the Stator for 12V first...then keep us posted.
I'm not positive, but there needs to be a 12V line running from the RUN terminal of the ignition switch to the alternator Stator terminal. If there isn't 12V at the S terminal then the alternator won't put out. Also, when the alternator is putting out then the Field terminal will show a voltage somewhere between 6 (low output) and 15 (high output)...if you have 12V to the S terminal, but nothing at the other then use a wire and connect the S and F terminals together to "full field" the alternator. If that turns the alternator on, then the problem is the regulator.
Kragen is usually good at testing alternators, so check the Stator for 12V first...then keep us posted.
Thread Starter
Racer
Joined: Jul 1999
Posts: 312
Likes: 0
From: Antioch, CA USA
Re: alternator problems (blackguard)
thanks for the replies. It has an external regulator(ford) and it was crapped out. It runs now. Gotta keep this car running till I get the vette done. You guys are great.
