I have a 1991 Dodge Dakota with a 5.2l/auto that is not charging. Battery tested fine. Alternator tested fine. Just replaced the battery cables both positive and negative. Cleaned up all grounds. The ECM is showing code 41. I've done extensive testing. The two smaller terminals on the back of the alternator show the same voltage, and they should not. I grounded one of the small terminals (Green Wire) and the alternator immediately began charging the battery. It does not charge otherwise. I checked the connection of the wire all the way to pin 20 on the ECM and it is good to go. When I ground pin 20 on the ecm it begins charging as well. So I assume the voltage regluator in the ECM is toast.. But I don't want to spend $200 on an ecm if I don't have to. Is there anything else to check or is this the proper solution? Can I crack open the ECM and fix it? I have moderate electrical skills and have done some ecu chipping before.

Any help is appreciated!

 

No you can not open up the PCM. The cheapest solution is to install an external voltage regulator. A 80's style Dodge truck one will work. They are $15 or so. As for how to hook it up do a Google search, I'm sure there are several links available.

I will move this to the 1st generation Dakota sub-forum.

 

Thanks for the reply. I've found a few how-to's on the external voltage regulator but it seems that no one has figured out how to do it without permanently living with a check engine light.. Anyone know a method that would allow the CEL to resume normal function?

 

if you need a new ecm I'll sell you mine for $40 plus shipping. just let me know...

 

I myself have been wondering about the cel after wiring in an external regulator. I did that to solve my charging issue. No issues with it since just gets annoying with the cel being on all the time.

If u decide to go that route, i can help ya through it if needed.

 

I'm encompassing the same issue exact same issue actually on the same year. I wired it up with a voltage regulator from like a 1988 Dodge stand alone style one. But I'm still not getting in charge. I'm not sure where I'm going wrong but what wires did you hook the two wires that go from a voltage regular too and what did you run the power signal wire from I got a ground going from the voltage regulator to the alternator so that we has a good ground on the case of the voltage regulator also I have one of the wires that comes out the back I think it's the bottom one that goes to the fuse box for now and then the other one goes to the one side of the field wires in the back of the alternator and the other one goes from top hen to the other field winding wire spot. Am I doing something wrong or is this just a bad one. Also I forgot to add the alternator was pulled out and tested and it works perfectly fine if I jump the field wires to ground and positive it does start charging

 

Did you see this? There's several other vids on you tube that address this too. Worth watching a few of them.

 

I got my idea to use external voltage regulators in the situation I'm in from the video but none of them actually give you the exact wiring from the very beginning to the very end of it and that's where I'm coming up with issues I watch one video and one video says do this I'm watching another video and it says to do that but I haven't found a video that showed the exact wiring of an external voltage regulator for a Mopar so you sent me a link or you posted a link I'm going to check that out that's why I was asking if you could walk me through just the two field wires where do they go grounding it to what what did you ground it to you know what did you use for the signal wire that kind of stuff I mean if I just get that stuff I can figure out the rest of it or I might be able to figure out the rest of it I'm going to be working on it today so I need to get it done so I can get paid for the job lol

 

Well Chief, I really wish I could help you more. I installed an external voltage regulator on my '93 a few years ago at the advice of HeyYou. After some fooling around I got it to work flawlessly. I ordered a kit from that Alternator Man but truthfully the regulator it came with is crap and I ended up with a New Old Stock off Ebay and it works great. As for the wiring I wish I could tell you. Two field wires go to the alternator (does not matter which goes to which terminal) and then they are a part of the harness that goes into the plug. You can buy that plug separately. I also added a relay so I could make sure the power cut off with the ignition. I photo'd my diagram...good luck making any sense of it. I wrote it and I can barely figure it out. Iff I sit there long enough I can figure it out. I'm no electrician. I also added another video...this guy gets into a bit more detail on the wiring. Not sure how much it helps you. I ground my regulator to the ground point on the alternator. I used a 10ish gauge ground cable - a beefy one cuz those regulators like grounds. Also sanded the paint off the fender where the reg mount screws go for added ground. Let me know if I can be of further help (or non help).

 

This is a simple diagram I was given for an external voltage regulator. The regulator is off a 1973 Mopar. Apparently everyone has them in stock. I got it and a pigtail for it and wired it up to run a 90amp alternator. I had to modify the pulley. Ended up being able to put the old 2pc pulley from the 50 amp OE alt on the new one which I ordered from the parts list for my dakota. The diagram is for a Dodge D50 (mitsubishi) but it should give you a good idea along with Brionze's info.
EDIT- Here is the quote about what regulator to buy "Buy a Chrysler External Voltage Regulator and Pigtail (any chrysler product 1971-1987) For simplicity and guaranteed results on getting the right stuff, buy one for a 1973 Plymouth Duster. This regulator and pigtail are always in stock at every parts store. You'll have about $20 invested in the Regulator and Pigtail."