Well I Tried installing an external Voltage Regulator and had problems. Quick recap. I have been having intermitent charging problems, have gone through everything except changing the crank sensor, PCM, ASD, Ohmed the entire wiring harness. So I thought I would bypass it with a VR. After installing it the check engine light came on. no charging noted on the dash voltmeter and the truck would not shut off with the key. The VR finally burned up and the truck stopped running. I anticipated having problems so I got 2 from the junk yard. re-read everything I could here and tried again. Same problem but I was able to shut the truck down by pulling the ingition wire to the VR. Now the check eng light is on and it is over charging, 16.5 at I idle and up to 19 while accelerating. The 2 codes that come up are Battery connection disturbed (12) and Gen field not switching properly (41) WHAT DID I DO AND HOW CAN I FIX IT. I have disconnected the battery numerous times and the codes still come up. I have disconnected the crank sensor to keep the batteries from burning up.

1993 4X4 Auto. Thanks for any help. R.

 

The code 12 means just what it says - the battery has been disconnected recently. That goes away in 50 starts or so. Code 41 is the important one, that means you have a problem in the field circuit. That "problem" is that you disconnected the factory wires from the field on the alternator (you did that, right?).

Try running a ground from the regulator case to the engine, that often cures an overcharging regulator.

 

I did not disconnect anything from the Alternator, I just attached the wires for the external VR over the existing connection on the 2 small posts on the alternator. I have a feeling that I burned out the new PCM (I believe you are alluding to this). I have become so frustrated that the truck is at a shop. It was there once before for this intermittent charging problem but they could not fix it. Any thoughts of where else to look would help. Thanks R

 

The factory field wires need to be disconnected. I don't think you fried the PCM.

 

i just installed an External VR this morning. i removed the factory "black box" off the back of the alternator, and set the VR up as described in the sticky. reattached the factory ground, and then joined a ground to the VR itself.

worked great, charging right at 14.2 volts.

I got mine new at napa, for an '85 d150, cost $12