Travs94Ram

Hey guys I did some well alot of searches on this problem and I had replaced my alternator right off the start cause it was not charging. Then once the new alternator was in and stared still no charging. I looked to see about maybe bad grounds and wires but grounds seem ok. I then checked the PCM and replaced mine with another one this evening in hopes this would fix the charging problem. The voltage regulator is in the PCM and still no voltage for charging the batteries. I have charged up the batteries so its not too much of a draw once started.

Like I said I did a search on past posts for this problem and still coming up with nothing. Any suggestions would be awesome. Oh also I did try to do the bypass from the alternator and instead of the very low voltage when the bypass was hooked up the charging voltage was 16+ and climbing so I shut it off as not to fry the batteries and new alternator.

RCW

Voltage regulation is through the ECM on the 94, but you can bypass the OEM system and use an external voltage regulator and fix the problem for cheap. Do a search on voltage regulator and you will land the posts on the part number and how it is done.

Travs94Ram

Yes thank you tried that but for some reason with the bypass the voltage did charge but kept on charging and did not regulate the voltage and was rising from about 10volts up to 16+ and was still rising when I shut off the truck. Going to check wiring and see if thats the problem.

patdaly

Any other issues, such as Tach not working?

Someone else wrote this, was so good I had to save it, might help you out:

I had to troubleshoot my charging system recently and came up with a fairly simple way to isolate the problem. Here is a step-by-step way.

First you will need a DVM to measure voltage. Also the batteries need enough charge to start the engine, so use a battery charger to get them charged enough.

The charging system is made up of the PCM mounted on the firewall, alternator, and don’t forget the 120 amp fuse in the PDC on the driver’s side fender well.

1) Start the engine and measure the battery voltage at one of the batteries. It should be more than 13 volts but probably less with a charging problem and that is why you are here.

Measure the voltage at the alternator output terminal (B+) leaving the DVM negative connected to the battery negative post. It the measurement is greater than 13 volts then the fuse in the PDC should be checked or the nut holding the heavy gage wire on the alternator is loose.

If you get this far then the next step is to measure the voltage coming from the PCM. The two small nuts on the back of the alternator are the ones to measure with the lower one positive and the upper one negative. These are the field terminals on the picture. If the voltage reading is greater than 8 volts the PCM is calling for full charge and your alternator is bad and not putting out. If the voltage is less than 3 volts your PCM is toast or the wiring between the PCM and alternator is broken. The normal voltage reading at the field terminals will vary from 3 to 6 volts when working correctly.

It’s always a good idea to clean battery terminals and check for bad grounds before spending money on replacement parts.

My alternator turned out to be bad and I had 9 volts at the field terminals. It was the diodes inside that were bad.

Travs94Ram

Problem fixed!!!! it was in the fuse box and the 30AMP ENG. CONTROL. was blown.

Thank you for your help! will keep an eye on it and see what could have cause it to blow. I will let you know if I find anything else out.

Thank you once again for all your help!

patdaly

Don't feel bad, I just lost a 50 amp fuse there, no corrosion, chaffed wires, etc.

They can be head scratchers. Glad you are up running.

Travs94Ram

yes nice to have it up and running again. Just wish fuel prices would stop rising!!!!

Travs94Ram

Thought problem was fixed but this weekend notice the voltage getting up there again when taking off from a stop. I can feather the pedal to try and not let it just up to over 16 volts and sometimes would max out just about 17 0r 18 volts. What had happened now is it keeps blowing the 30 amp engine control fuse.

I did replace my PCM with one from another truck but going to put mine back in cause dealership says mine might need to been re flashed with my trucks specs and vin # info.

I have to get my PCM shipped up to me and go get more 30 amp fuses but sure hopes this fixes the voltage problem. I sure hope its not a bad ground cause trying to fix your truck in a parking lot in the rain is not fun!

Any help or suggestions is greatly appreacited thanks fellow DTR

infidel

Do as RCW said and install an external regulator. Any 12 volt regulator will work. Instructions here are for '92-'93 but will work on any Ram https://www.dieseltruckresource.com/...n&onlynewfaq=1

Travs94Ram

Thanks but have tried a few of the external regulator. For some reason when hooked up it over charges and the voltage goes over 16 volts and keeps going up so I shut the truck off as to not kill the batteries or new alternator.

infidel

That doesn't sound possible.
Did you disconnect the the stock wires from the PCM?

Travs94Ram

yes the wires were disconnected and taped up but for some strange reason the voltage went above 16 volts.

Haulin_in_Dixie

If it is not charging right with the external regulator you have something hooked up wrong. Once set up it is a fool proof system. I have two of them with the external, one needed it and the other got one while doing some other work just to be safe. I have also set up over a dozen of them on other vehicles and not just Cummins diesels. You have a "dumb" alternator and all it takes is a regulator to feed the field voltage. I will suggest that you also run a ground wire directly from the alternator to the base mount screws of the regulator. I had one that would not operate right without that.

Travs94Ram

Ok thank you I will try that. I hope to get my PCM tomorrow and hope to put it back in and take out the replacement and hope that works. If it doesn't I will try that. I did not try the gound directly from the alternator to the base mount sscrews of the regulator.

Travs94Ram

Seems once I put in the original PCM and replaced the 30 amp fuse everything went back to normal.