My buddy has a 89 dodge w150 gas truck and it wont charge. I changed the alt and still no charge. I did the voltage regulator conversion as his was controled by the pcm also. It is charging fine now but I cant get the check engine light to go out. I cleared all the codes and the light comes right back. The code that is turning on the light is something about the alt field wiring is open or shorted. I had that code before the regulator. Have you guys had any issues like this I know that because it is gas somethings aint the same but it is driving me nuts.

 

I don't think you are going to be able to make the PCM happy. The field wiring IS open because it's not connected to the alternator anymore.

 

Just a thought. Can you splice in the field wire going to the PCM to the field wire coming out of the alternator and make the PCM believe its working?

 

have owened many 89,s all where external reg

 

OP says it's a gasser.

 

Try hooking the old field wires to a small light bulb, that may be enough to trick the PCM. Don't know if it will work but worth a try.

 

thanks guys i think i am just going to leave it alone it is charging i might leave well enough alone. before i screw up something else.

 

I have this same issue on my '93 D150 (gasser)....I read somewhere else that a small resistor between those two fields will fool the PCM and turn off the MIL. Thing is, there are a thousand different resistors....which one is needed?

 

Just hook a 12 volt light bulb or a relay coil across the leads.
That should make it happy.

 

Disconnect those wires and put an ohmmeter across the two terminals and take a reading. I'm thinking it will be a really low number since you are in effect checking the continuity of the coil.