[Bob Lincoln]

Having the regulator inside the ECM improves its reliability by taking it away from the heat and electrical noise of the alternator. It also improves power quality by having it closer to the circuitry that uses it.

How did you determine that the regulator circuit is bad?

 

[Russ67]

Thanks for your reply, Bob. I don't fully agree that having the regulator in the ECM improves reliability or power quality, though. I suspect that it was more of a cost savings issue than a quality improvement. I've had many Mopars over the years and after the era of the mechanical regulators I have not had one regulator go bad.

My son was using the truck when the problem showed up. He removed the alternator and had it tested at an auto parts store and it tested good. When he got home, as a caution I removed the brush holder to check the condition of the brushes and they are fine. I don't have a service manual for this truck but I do have a FSM for a 91 Dodge Shadow that I used to own which had a similar alternator and regulator setup. I followed the trouble shooting procedure in the manual and determined that the regulator was at fault.

Because of the age and fairly low value of a 90 Dakota I suspect that others have tried some alternate means of getting around this problem other than replacing the ECM. I don't want to modify the mount and install a different style alternator so It appears to me that adapting an external regulator to the current alternator would be the easiest and least expensive way to repair it. I am going to try it and just curious to see if it has been done by someone already.

 

[John Wood]

I'd try some junk yard searches (on line) or even EBay for a used replacement ECM. You might find that these are not as expensive as you think. Perhaps Rock Auto has a remanufactured unit. It is worth checking into before attempting the external electronic retrofit. The external electronic regulator can be made to work. A few have done it here on the EEK cars, but you may end up with a check engine light that can't be easily eliminated. By the time you buy the 3 wire plug pigtail (available from NAPA) and the actual regulator, you might be close to the cost of a reman ECU. I hear that it is critical that the electronic regulator case be grounded well or you can cause an over voltage situation that can fry the ECU.

 

[Russ67]

Thanks for the advice, John. I've done some searching for a new or used ECM but so far haven't located one. It's a 90 Dakota, V6/automatic, a/c with throttle body FI. I've seen ECM's for other Dakotas and now I'm wondering if the one for this model is unique to only 90 models. If I decide to go with an external regulator it would be from Pull-A-Part and likely less than $10 with the plug.

You have some high-mile Mopars there. The most I've ever put on one was 201K. It was a 1976 Aspen station wagon with slant six and overdrive and still ran and performed good when I let it go. I just got tired of shifting gears and bought a Diplomat with automatic.

 

[valiant67]

There are bunches of them on eBay right now.
And more on
http://www.car-part.com/
The computer is unique to your 1990 model year, auto vs manual transmission and federal vs. California emissions.

 

[Bob Lincoln]

Not to be argumentative, but an external regulator is cheaper than an internal one. It was moved inside as a reliability improvement. I'm an electrical engineer with nearly 30 years of experience, especially in reliability of semiconductors. Heat, contaminants and vibration are all reduced by moving the regulator inside the ECM.

It's very possible that it's not an ECM failure, but rather the connections to the ECM. These can get oxidized, plating wears out, and the contacts relax their spring tension until they no longer make good contact. I'd clean and examine each pin on the harness side and on the ECM side, repack with dielectric grease and reconnect. Then I'd backprobe the wiring connections with a multimeter, all before replacing the ECM. It does happen quite a lot, that an ECM will be replaced and blamed, when in fact unplugging and plugging its connector removed enough oxidation to restore a good connection, without the ECM being bad in the first place.

 

[GLHS60]

Check this out.

Thanks
Randy

http://www.turbo-mopar.com/forums/knowledge.php?title=Electrical-Systems:How-to-convert-to-an-external-voltage-regulator

 

[Bob Lincoln]

Hmm..

"I installed a brand new Bosch Nippendenso-style alternator" - It's one or the other, and shown is a Nippondenso style, not Bosch.

But he lost me right here: "My battery charging issue was one of three things, alternator, wiring, or voltage regulator. So rather than test each, I just swapped everything."

 

[AllanC]

First let me vent: Why in the world did Chrysler change from their own [background=transparent]dependable[/background] alternator with an external regulator to a very expensive Bosch alternator? And why did they incorporate the regulator into the engine controller?

Besides reliability and isolation from contaminants and heat, moving the regulator onto the circuitry that controls engine management allows the engine controller software to compensate for varying voltage levels encountered on the vehicle. At idle and high electrical load system voltage will be lower than at highway speed and light electrical load. Higher voltage means the fuel injectors will open quicker (in milliseconds) than at a lower voltage. This affects engine emissions so the software is designed to compensate for this. Engine emissions are so stringent today that engineers have to account for every possibility in reducing "bad things" exiting from engine exhaust.

I would agree with Bob L and say that engine controller failure is rare. It is much more likely that a connection develops corrosion, rust ,dirt, etc which impairs the electrical signal and makes it look like the electronic controller has failed. I would check and re-check all connections and clean thoroughly before starting with cobbled work around solutions to problems.

 

[John Wood]

So far I've had two internal regulators fail on EEK cars. One was on the 87 LeBaron and it was the Power Module. The other was on my 91 Sundance which uses an identical ECU as the 91 Spirit. Interchangeing the units between the vehicles showed that the vehicle with the suspect ECU failed to charge. All connectors were cleaned and swept and a $25 junk yard unit immediately resolved the problem. I agree it is a rare failure but it does happen. Definitely clean all connectors and perform continuity checks to be sure.

 

[awyseguy]

I'm not sure on that particular alternator or application; but I have bypassed the integrated regulator on a couple in the past.. I changed my 86 Shelby Charger to an external regulator around 1996.. It was a simple fix, and I even hooked it in parallel with the ECU so it thought it was still doing its job. I did have one that would not work with both connected though..