Hi just got a d350 and I tested the alt and it only was charging at 12v and I tested the battery and it tested 12v amd I was falling I know the batter is shot but why wont the alt charge anyways?

 

is this at idle or at higher rpms because Im not sure if the 89-93 had voltage regulators. and do you have a load tester.

 

I dont think they have a regulator and it was at idle

 

the 89-91 had external voltage regulators on the fire walls. the 92-93 have them built into the PCM. mine went bad and i dont have 600$ to replace an entire pcm for a bad voltage regulator so i bypassed it and spent 18$ at autozone and it fixed the problem but it doesnt seem like your symptons are a bad alternator. if it was a regulator you would still get 14.6 volts out of the alternator. take it to a local parts store and have them bench test it.

 

Don't rule out the crank position sensor as if there is oil or dust on it, it will cause same problem

 

Who told you it would cost $600? Rockauto rebuilt mine for $215 two years ago still working fine. Remaned mine because everything stopped working cruise AC and I'm not rigging anything if possible. Worked at the dealer long enough to know its easier and cheaper(most of the time) in the long run to fix it right the first time