Alternator Not charging
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Post Fiend
Joined: Feb 2001
Posts: 6,624
Likes: 8
From: Missouri
Alternator Not charging
My alternator light came on in my truck and I managed to get it home but it would not start so the light is not lying to me as it has before. I took the alternator in to autozone and they showed me it was putting out 15 volts. I then swapped the voltage regulator and that didn't fix it either. I re-did the connectors on the alternator to ensure they were in good order. The battery does not discharge while it is sitting so it isn't a major short and all the wires look good. Any ideas why it isn't charging? Seems kinda wierd to me. I have been thinking there are some diodes in the alternator that are out and not letting it cooperate with the regulator. Anybody know where the wires go from the alternator so I can ohm them out? Thanks.
Post Fiend
Joined: Feb 2000
Posts: 5,130
Likes: 8
From: Brea CA
Alternator Not charging
Sean, try a full-field test first. Unplug the connector from the regulator and take a jumper wire from the "F" wire to the "A" wire. Start the engine and measure the battery voltage, it should go up to around 16 volts. This will test out the F and A wire, fuse link and alt. output.
I've made a little test jumper just for this, a short length of 18ga wire with spade lugs on each end. Unplug the connector and insert into the A and F slots. You get a little spark and the alt. will whine as it's fully loaded.
If it tests out ok, then all that's left is the regulator. Check and make sure the regulator is well grounded through the mounting screws. Ok I'll stop editing now and let you do your thing.
Barry
I've made a little test jumper just for this, a short length of 18ga wire with spade lugs on each end. Unplug the connector and insert into the A and F slots. You get a little spark and the alt. will whine as it's fully loaded.
If it tests out ok, then all that's left is the regulator. Check and make sure the regulator is well grounded through the mounting screws. Ok I'll stop editing now and let you do your thing.
Barry
Last edited by BB; Sep 21, 2003 at 04:25 PM.
Thread Starter
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Post Fiend
Joined: Feb 2001
Posts: 6,624
Likes: 8
From: Missouri
Alternator Not charging
I just looked at the other regulator and I figured out what A and F were. I took the alternator back to autozone earlier to get it warrantied out just to make sure. When it quits raining I will give it a shot. Thanks, that is a pretty neat trick.
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Post Fiend
Joined: Feb 2001
Posts: 6,624
Likes: 8
From: Missouri
Alternator Not charging
Just out of curiosity I got the new alternator and the posts are marked. STA means stator, GRD means ground and BAT means battery but what does FLD mean? Is it field? Gonna install it in the morning.
Last edited by Ratsmoker; Sep 21, 2003 at 07:54 PM.
Post Fiend
Joined: Apr 2002
Posts: 7,157
Likes: 1
From: Central Kali
Alternator Not charging
fld does mean field. The field output from the regulator is what makes the alternator start charging the battery.
I check mine by measuring the voltage on the field term. If you have around 11 or so volts but the battery is 12.6 or less, the alternator is bad.
No voltage at the field term means the regulator or wiring is the problem. Trucks with an ammeter use the S term on the regulator. With the key on, 12v on the S tells the regulator to energize the field. Trucks with a bat light use a different and slightly more complicated approach.
The diodes in the alternator are there to rectify the 3 phase output of the stator to dc. I once had 3 of the 6 diodes open. The output was 14 volts but it would not supply the rated current.
I check mine by measuring the voltage on the field term. If you have around 11 or so volts but the battery is 12.6 or less, the alternator is bad.
No voltage at the field term means the regulator or wiring is the problem. Trucks with an ammeter use the S term on the regulator. With the key on, 12v on the S tells the regulator to energize the field. Trucks with a bat light use a different and slightly more complicated approach.
The diodes in the alternator are there to rectify the 3 phase output of the stator to dc. I once had 3 of the 6 diodes open. The output was 14 volts but it would not supply the rated current.
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