PCM / Alternator

[JCrank]

Can anyone instruct me how to properly bypass the PCM to make my alternator work properly ?

 

[1stgen4evr]

You could get the wires from an 89 or 90 and retro fit the volatge regulator circuit. Chrysler voltage regulators are not the finest equipment in the world either. I have an add on that I got from the starter/alternator rebuild shop which eliminates the PCM as to alternator control. It is a very small unit which mounts on the alternator. No doubt there is more than one type of aftermarket device to do this. I will see if I can get a part number for the one I have.



From my experience, you have a greater issue with the PCM if that part of it is failing. Does your transmission shift properly as to OD function? Mine didn't and the alternator was intermittent. Work sometimes and not sometimes. The AC is also under the command of the PCM. That was begining to malfunction as well. I have done away with the PCM and the truck is better for it.



James

 

[Paychk]

These should help, sorry it took so long, had to do some digging & searching.



https://www.turbodieselregister.com/forums/showthread.php?threadid=81095&highlight=alternator+wiring



https://www.turbodieselregister.com...644254&highlight=voltage+regulator#post644254



https://www.turbodieselregister.com...35066&highlight=external+regulator#post835066

 

[Old Smoky]

The crank position sensor can also cause charging issues. Mine failed about two months ago.



Mike

 

[DKasper]

Hey James -- how did you rig the speedometer? I was looking through the PCM outputs in the manual the other night and I think I've figured out how to get around everything I need but the speedo.



Thanks!

Dave

 

[JCrank]

I found out from the previous owner yesterday, that he had repalced the PCM within the last six months and also the crank position sensor and alternator just prior to that. Could there be something killing the PCM ? Everything else is working fine. I traced the blue and green wires from the alternator all the way to the PCM and have continuity all the way to the PCM connector. I've checked all connections everyone has suggested as well.

 

[1stgen4evr]

every thing but the speedo

Dave, I have not addressed the speedo. The PCM is still on the truck so I suppose that I have not "done away with the PCM" as I stated. But I don't have an issue with the AC, Alternator or OD. The AC, Alternator and the OD are the only thing I have re-routed. Not sure what I will do when the speedo quits. I will look at the 89 and see if there is an apparent way to incorporate that system.



James

 

[JCrank]

If the speedometer, tach, a/c, and/or cruise control isn't working it could be the crank position sensor. Check the connector for same at the front of engine near first valve cover. If this is OK, then check to see if one terminal has continuity (ground),the other two terminals : one should show 8 volts and the other should show 5 volts (sensor signal terminal). The crank position sensor had been replaced on my truck. It was improperly positioned due to the spacers not being reinstalled, the sensor was positioned over the belt instead of the damper. Sensor to damper gap should be . 050" (use brass feeler gauge).

 

[DKasper]

Thanks James -- sorry guys, I didn't mean to hijack the post.

 

[CGauthier]

It is to my understanding that the speedo is not driven by the PCM... .



CG

 

[Paychk]

Carl is right, the signal from the speed sensor goes to the speedo head and that is all it takes for that to work. The PCM does read the speed sensor, but that is so it can operate the cruise control.

 

[1stgen4evr]

PCM does- - - - so it can operate the cruise control

Ah ha. So that is the reason I still have the speedo. The cruise was the first thing to go and it was so long ago that I had forgotten. I have used a stick to accomplish cruise once or twice.



James