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Dodgerench, ASE Certified Technician
Category: Dodge
Satisfied Customers: 3406
Experience:  30+ years Dodge/Chrysler exp., ASE Master with L1 certification. Driveability/ combustion specialist
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my 1991 dodge dakota v8 does not charge I believe it is the

Resolved Question:

my 1991 dodge dakota v8 does not charge I believe it is the voltage reg in the ecu. Can I wire an external voltage reg in and how
Submitted: 7 years ago.
Category: Dodge
Expert:  Dodgerench replied 7 years ago.
HiCustomer welcome to Just Answer!.

Check this for me first if you would. Start the engine and check the two small studs on the back side of the alternator for voltage. These are the field control terminals, BOTH of which will have equal voltage if the PCM has lost its ability to regulate the charging system.

If you have only one source, check to see if the side with NO voltage has continuity to battery negative. A good method for this is to use a 12v test light connected to battey positive. If it lights when touched to the dead terminal, the PCM is OK and the alternator is at fault.

I can describe a way to add an external regulator, but there's a very good chance that you'd have to live with an always-on CHECK ENGINE lamp from that time on.

Speaking of CHECK ENGINE lamps, it might be worth checking codes before we get too far. You can have the engine scanned or use the "flash code" method, something built into the truck's electronics. Here's how it works...

Roll the key from off to on three times, leaving the key ON.

Watch the CHECK ENGINE lamp as it does a longer than normal bulb check (close to 5 seconds) and then goes dark.

When the CE light comes back, it will be flashing, so be ready to keep count.

The pauses between flashes tell you what to do. Short pauses mean you should continue counting... this digit isn't done yet.

Longer pauses mean the digit is completed and you're moving on to the next one.

All trouble codes are composed of two digits, like 12 or 55, so you will always have an even number of digits once the flash code process is over.

Repeating the process 2-3 times is highly recommended if you're not a flash code veteran... codes such as 12 often become... "3" if the pauses aren't recognized.

Let's see if there's something we can use in there, but if the battery has been disconnected or gone dead codes may be lost... that's what a code 12 indicates, recent loss of memory by the way, with 41 being a charging system code.

Check these few things out and we'll move on from there.
Talk later,

Customer: replied 7 years ago.

I will check this and get back to you


Expert:  Dodgerench replied 7 years ago.
I might not be available tomorrow or even the next day, but feel free to post your results any time.

By the way, if the alternator brushes are at fault, a sharp tap with a hammer to the alternator case will often revive the unit in many cases for diagnostic purposes.

Good luck!

Edited by Dodgerench on 10/12/2009 at 5:05 AM EST
Customer: replied 7 years ago.

Hello Dodgerench I finally got around to checking the alternator and codes, here's what I found. The two small terminals on the alt both tested the same at 9-10 volts. So then I checked for codes and I got a 12 followed by 41 then 55 so hopefully that info helps you to help me thanks alot.

Expert:  Dodgerench replied 7 years ago.
It does appear your PCM's internal voltage regulator quit on you... and it knows it. Code 41 is a charging system code.

We can go ahead with the external regulator if you want, but I'm pretty sure you will have a perpetually-burning CHECK ENGINE lamp. Is that OK?

Customer: replied 7 years ago.

Its an old farm truck nearing the end of its existance I will deal with the light


Expert:  Dodgerench replied 7 years ago.
Understood. I'll get to work on it but may not get the post back to you until late tonight or tomorrow morning. Is that OK?

Customer: replied 7 years ago.
Thats fine I'm not in a hurry I have other vehicles to drive
Expert:  Dodgerench replied 7 years ago.
Great. Talk in a bit!
Expert:  Dodgerench replied 7 years ago.
I think the easiest regulator to hook up would be the old Chrysler electronic unit we used from the 70s into the 80s. It used only two wire connections, plus the case ground which would be the third. Here's a quick picture of the regulator and connector for reference as we work...


The tricky part might be finding the connector for this regulator, but there should be plenty around the wrecking yards. If you get stuck, I'm sure you could figure something out... like using a solderless bullet electrical connector to push over the stud pins in the regulator front. Then fill the cavity with silicone RTV to create your own connector... stuff like that. =/

Your field control wiring at the alternator hold everything you need.

The blue wire is a key-on voltage source which is used to power the brushes and can also be used as the voltage reference source on your new regulator. It's not an ideal choice, but it's quite simple and will work fine for your purposes. Although there will be some voltage drop on the circuit as charging loads are high, as the system gains charge, loads on the circuit will drop and it should produce something very, very close to what actual battery voltage is.

The regulator can go practically anywhere, but for practical purposes, place it near the alternator. You'll need to ground the regulator case, which can be as simple as just bolting it to anything metal underhood... either on the engine or on the fenderwell. Remember that it must be grounded, so sand away paint where ever the connection will be made.

Locate the blue and the dark green wires that lead to the back of the alternator.

The blue wire is your key-on voltage source (called J2) and the green wire is the field control.

Find a handy spot to strip the blue wire so you can solder a jumper wire onto it. Use at least 16 gauge wire and run this to the J2 (blue) terminal of the voltage regulator. Note that the connector diagram shows you the open (terminal) side of the unit, so things are reversed.

The blue wire needs to connect to the alternator and to the regulator because it supplies power to the brushes and a voltage reference for the regulator.

The green wire from the alternator can be cut off at this point for connection to the regulator. It runs to terminal 20 of the PCM, so you could even mount it way back there if it would be handy, using the original factory wiring. Terminal numbering can be found on the 60-way PCM connector by removing the black plastic wire shield on the back side of the connector.

Connect this wire to the appropriate terminal of the regulator, bolt it down and away you go! These regulators are super-dependable, so I'd have no problem with buying a regulator at the junkyard and just help myself to the connector. You'll find this setup in any carbureted full-size truck and car all the way up to about 1987. They're everywhere.

Write if I haven't confused you enough!
Dodgerench and other Dodge Specialists are ready to help you
Customer: replied 7 years ago.

I will give it a try it looks simple enough I'm sure I can handle it

I will get back to you when this is complete and we see how it works

It might take a couple days to get parts and get time to do this



Expert:  Dodgerench replied 7 years ago.
You're quite welcome, Duane. Good luck!

Customer: replied 7 years ago.

hello again I got a voltage reg and harness like you said from the aftermarket parts store in town for $12 total and wired it in today. It works great Thanks again for all the help.


Expert:  Dodgerench replied 7 years ago.
That's great news, Duane! Thanks for hanging with me!
Does the CHECK ENGINE light stay on?


Edited by Dodgerench on 10/15/2009 at 12:41 AM EST
Customer: replied 7 years ago.
yes its on all the time I'm considering disconecting it?
Expert:  Dodgerench replied 7 years ago.
Nah, keep it around in case you need a flash code some day. Tape would do the trick for now!

Customer: replied 7 years ago.