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 started 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.

torquefan

1) with the key OFF, check for power to the heavy "charge" wire on the back of the alternator. It should have power. If not, check for a blown charge fuse in the PDC, or an open charge wire between the alternator and battery.

2) there are 2 smaller "field" terminals on the back of the alternator. With the engine RUNNING, there should be close to 12 volts between the two. They should light a test light if one is hooked between the two terminals. One is power (from the ASD circuit), the other is ground (from the voltage regulator circuit of the PCM). If you can't light a test light between these two terminals, you need to find out if it's the power or the ground that is missing, and go from there.

The above is basically all you need to diagnose the problem, assuming you have a drive belt, and it is turning the alternator. Let me know if you need further direction after testing the above.

On edit: it's a long shot, but you might as well be sure the alternator case is grounded well to the engine. Just a quick stab with a test light from battery positive to the alt. case should be all you need to tell you there is a reasonable ground there.

Note: I should add that for these tests I am referring to an analog test light with a regular bulb, not an LED tester.

Travs94Ram

Thank you I will give this a try in the morning. I have the truck at my shop right now. I was thinking it might be something with the wires power or ground since many say the wires break inside and is not visible. I will let you know how it goes tomorrow.

All the suggestions will be tired and hope once I find the problem will post so someone else does not have to go though all this guess work and hopefully narrow the search down and hopefully to a cheap or free fix! I have a new alternator and another PCM and these are not cheap parts to find out the problem was not fixed.

Lil Dog

Is the tach steady? The crank sensor might also cause the same problems fooling the PCM into thinking the engine isn't running yet.

Travs94Ram

Yes all the guages are working tach and everything with the guages are working as they should. Going to check the crank sensor and grounds to see if thats the problem.

vzdude

Ran into one of those the other day! What a pain in the rear! I have one from Snap On that has both a red and a green LED in it and you have to hook up leads to + and - . Put on some trailer wiring the other day and it came with a cheesy led test light so I figured it would save me a trip to the shop for mine..........took me a minute to figure out why I couldn't see if I had a ground at the trailer wiring or not! Can they be that much cheaper than a little light bulb?

Travs94Ram

yea for sure its sure time consuming to check but guess wires get old and break on these trucks and could make life a real pain. Still looking for the problem.

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!

torquefan

Congrats! Glad you found it. Hope that's the end of the problems.

torquefan

I know what you mean. I've gotten a couple of those cheesy little testers that came with trailer wiring kits. I always wonder if I should even bother keeping it around for a spare or not.

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

Travs94Ram

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

waldersha

I know I'm dragging this one up from deep down, but I'm having issues with my charging system. I went through the tests above.

I have power with the key off to the "charge" wire of a little over 13 volts.

When the engine is running, there is only about 3.5 volts between the two terminals on the back. If the A/C is on, it is about 5 volts.

The alternator case seems to be grounded ok, between the positive battery cable and the alternator case shows battery voltage. All the gauges and tach seem like they are working ok.

What's next?

Randall62

AlpineRAM

Or you can go with an external charging regulator from Autozone.. it will charge if the engine is running, regardless of tach signal and all the other things that can go wrong with the stock charging system.
See:
https://www.dieseltruckresource.com/...ummins-120632/