Why is my charging system is not working? How can I fix it?
The battery and alternator both tested
good. The alternator fuse is good. Even
Replaced pcm. Yet no luck. What am I
missing? Please help.
so what is actually happening? if the battery is good and the alternator is charging, then everything is working. Is the battery dying over night or something?
The alternator is not charging
I replaced it. And the battery
The voltage meter reads 12ish. I've researched this problem and it sounds like it's the voltage regulator, inside the pcm. So I replaced the pcm. Yet it still didn't fix the issue
Take the alternator out and have it bench tested. This takes the Pcm voltage regulator out of the equation. It is possible that your new alternator is bad. Have had that happen to me. Also, make sure all wiring is good especially from the pcm to the alternator. There may be a way to test the pcm voltage regulator, that would be ideal, but it may require sophisticated testing equipment.
Have the battery charged and load tested. It could also be bad.
check your 140 amp charging system fuse under the hood.
I am having the exact same issue with my truck. New Alt, a new battery which tests good, PCM fuse #23 is good, and I bypassed the fusible link from the alt to battery and it is still not charging. I have not replaced the PCM yet. When I start my truck my alternator shows it is charging on the gauge at idle but as soon as I put it under a load by driving or by turning on lights, heater, radio, etc it goes to 0 and my check gauges light comes on. I am concerned it is a ground, the PCM, or a battery temp sensor issue but I would like to know how your issue turned out before I buy a new PCM.
Soaleman- I am having the same issue. How did you fix it?
I am also have the same issue with my 03 Dodge ram 2500 with a 5.7L battery is good and a brand new alt. I turn the accessories on and the gauge shows voltage. I start the truck it looks like it's going to work then it drops to zero and says check gauges. What is the problem.
I actually bypassed the PCM with an external voltage regulator from a 70s dodge truck and it works great. $35 bucks for the parts and about a hour to set up. Plus you can always put it back to stock later. The PCM was bad and it was telling the alt to stop when it went under a load. I talked to a guy who sells PCMs and he said the diode went out.
Yep that's what I did, and it still didn't charge. So I actually took the alternator off and had it bench tested. Failed. Got a new alternator and external voltage regulator works. Getting a new PCM now though because of some old connectors that have corroded.... Mud is fun for 5 mins but it is probably the worst thing you can do to your rig hahah!
When I jump it off the check gauge come on
Replace the black cable that runs from alternator to fuse box under hood
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