have 98 12 valve started not charging good all the time unless i got out and pulled against the voltage regulator on back of alternator then it would charge for a while.Thought one of the field post was loose tried to tighten and twisted on of the post off. had another alternator put it on still no charge both of them only putting out about 12.5 volts. change backs on them and still no charge took to auto parts store tested it and said it was good. have cleaned all battery terminals and charge batteries full still low charge any help could it possibly be PCM.need quick response if anyone can help Thanks

 

could just be time for a reman some times you can hit them with a mallet and they will work but that just says its time for a new one .you can also rebuild them your self. check ground wire to and use dielectric grease on the fitting

 

ok thanks Parts store tested Alternators checked out ok

 

You may have a voltage regulator problem. The VR is in the PCM. Do a voltage test on the field wires with the engine running.

On my 96 I get 9.45 volts on the top terminal, blue wire, and 13.83 on the bottom terminal, green wire, at idle. I get 13.83 volts at the battery at idle.

The top wire is the ASD relay sense and the bottom is the field driver. You need voltage on both. As I understand it, the field driver excites the alternator to start charging and the sense wire is used to maintain the voltage limits.

If the VR is bad it requires a PCM change or you can add an external VR.

 

I suggest you do not get a remanufactored. Get you OEM rebuilt if that is needed.

Floyd