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if it isn’t one thing it’s another. About a year ago I changed the alternator in the truck to a 3G alternator. I got the alternator out of the Taurus and his worked fine until recently. When it stopped charging. It would charge 14 1/2 V upon initial startup then after about 10 minutes would cut out and it drop down to 12 1/2 V. it would still run and drive, but it was surging and stumbled off idle. Drove it for about a half an hour and watch the vault gauge go from 12 1/2 V to roughly 11 1/2 V. This is when I went to get a new alternator, remanufactured, right out of the box. Installed new alternator and the truck ran fine for about 10 minutes then the charging went back down to 12 1/2 V from about 14 1/2 V. I am stumped at what this problem is and I fear. I just blew out a new alternator. I do have an HEI distributor and wondered if I burnt out the pick up from the lower voltage. Any help and guidance is appreciated. I do have a relay in the fuse of the alternator field wire and they are both as far as I can tell at least the fuse is good. I also use the painless wiring wiring kit for when I did the alternator.
if it isn’t one thing it’s another. ... etc ... This is when I went to get a new alternator, remanufactured, right out of the box. Installed new alternator and the truck ran fine for about 10 minutes then the charging went back down... etc ....
Auto parts stores will test alternators for free. I delivered parts mostly, but even I did counter work if not delivering, and more than once I replaced a faulty testing new or recently bought alternator. Even if the customer lost the receipt, we could look it up usually, for warranty issues, but it is quicker with a readable receipt..
Any help and guidance is appreciated. I do have a relay in the fuse of the alternator field wire and they are both as far as I can tell at least the fuse is good. I also use the painless wiring wiring kit for when I did the alternator.
Interesting problem.
The quick fix is just to connect the fat yellow wire on the voltage regulator directly to output post on the alternator.
Also check that.....
The white wire on the volt regulator jumps over the the stator output.
The green wire on the volt regulator is the input to bring the alternator online. Once it's producing output voltage it isn't needed anymore. It's working as it should as the alternator comes online initially.
The fat yellow wire on the voltage regulator is an input. It is the "alternator field" input as you call it. It is constantly needed to provide the field (rotor), the needed voltage / current. It is also the source for the alternator reference voltage. If you lose this input the alternator doesn't provide an output.
Also , low voltage will not cause things to fail, but over voltage can.
Good luck, Jim
Interesting problem.
The quick fix is just to connect the fat yellow wire on the voltage regulator directly to output post on the alternator.
Also check that.....
The white wire on the volt regulator jumps over the the stator output.
The green wire on the volt regulator is the input to bring the alternator online. Once it's producing output voltage it isn't needed anymore. It's working as it should as the alternator comes online initially.
The fat yellow wire on the voltage regulator is an input. It is the "alternator field" input as you call it. It is constantly needed to provide the field (rotor), the needed voltage / current. It is also the source for the alternator reference voltage. If you lose this input the alternator doesn't provide an output.
Also , low voltage will not cause things to fail, but over voltage can.
Good luck, Jim
I tested the wires and do have 12v on the yellow with key off and 12v on the green/red with key on. With the connector plugged in and the white (S) connector has no voltage.
I tested the wires and do have 12v on the yellow with key off and 12v on the green/red with key on. With the connector plugged in and the white (S) connector has no voltage.
Those are all good results.
I think you have to wait 10 minutes, for the yellow wire to lose voltage. This is the mystery part.
Jumping the yellow wire to the output post is just for troubleshooting, to see if it fixes the problem.
Good luck, Jim
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