I have a 94 Dodge Dakota Sport with the 3.9L V6. The truck has been overcharging for quite sometime and I want to fix it before I do damage. I took the battery off while running the truck and still overcharges. Is the voltage regular built-in the alternator? I always been told is if its overcharging, its the alternator/voltage regulator. If its de-charging, its the battery.

Any help is appreciated.

 

I do believe the regulator is part of the alternator. The external voltage regulators were found on the carbed Daks. Autozone might be able to help you with testing your alternator

 

I had a similar problem in my dakota turned out that the voltage regulator is part of the trucks computer. I went through 3 alternators in a period of a week(all under warrenty). I had to replace the computer they run about 100 bucks.

 

Just replace the alternator.

 

So overcharging is caused by the ECM? Will overcharging pop the ASD 30A fuse in the distribution center?

I'm getting 16.78v at idle at the battery.

I pulled the alternator - Advance couldn't figure out how to hook it up to their tester with the "universal" plug assembly, NAPA has a brand new tester (mine was the 4th one they've tested on it) and it passed 2 of the 3 tests but said idle voltage was 8.something and AutoZone tested it 3 times and all 3 said good.

If I put it on the truck it pops the ASD fuse & the truck dies - I replaced the ASD fuse with my fluke and I get 11-19amps, shouldn't be enough to pop the 30A but it does. Volts at the battery while charging are 16-18 (too high I know) and with the truck off I'm at 12.9 - the battery is 5 years old but has never run dead or low.

If I pull the ECM wires off the alternator but leave it hooked up to the battery the truck starts & runs fine, but of course it's not charging.

No codes other than 12 (ecm power loss) and 55 (end of codes).

Any ideas?

It's sounding to me like the ECM, conceivably some sort of short in the field controls? I'm going to swap the wife's 120A unit out of her Durango to test it - I just need to make an adapter harness to plug the computer in to it.

Oh yeah mine's a 95 Dak 3.9 5spd, 2wd.

Any ideas?

 

It may be the computer. But since the Alt did fail 1 out of 3 tests I would say get it tested again. Take it to somewhere else that can test it. Get it done a few times.

Also you can check the FAQ for the service manual, it has a section for Starting/ Charging. That may a have a diagnostic chart for you.

You may have a wire problem with the fuse constantly poping.

Also don't be scared to start a new thread instead of pulling up a 1 year old thread.

 

Super new here and finding my way around. I have a 89 Dakota Sport that went in the shop last year for power surges. I personally replaced map sensor and acu (it wasn't it)., couldn't find what was wrong. Mechanic at the shop replaced the ECU he told me "mice went into it". Got the truck back, running fine for 2 weeks, then no start (no spark) nothing while at the store. It went back to the shop, mechanic said the new ECU was faulty, he reordered and replaced. He also replaced my brand new coil (somehow they managed to fry it) replaced my battery told me it was dead (1yr old optima red top). Got the truck back and vehicle is now overcharging the battery (new alternator month old btw). I've replaced it again with a another new. Battery still overcharging. Been searching the internet forever as you can see. My question is how many different ECU's for the 89 Dakota sport? Could the ECU be the problem? Fixing this truck is my first option. Second option fixing my 96 Dakota 3.9 Mag (automatic) trans slipping. Pretty much tapped out on funds and need a vehicle quick. Any help would be awesome, in return you got yourself a kick *** bud in Hawaii.

 

I believe the 1989 should have a replaceable voltage regulator.
http://www.oreillyauto.com/site/c/se...989&vi=1087398 (For a 1989 3.9L V6)

 

That's quite interesting, the only thing is I'm unable to located that anywhere on my firewall. Another new alternator and battery installed. Voltage meter on dash still peaking. Could there possibly be a ground problem? (excuse my ignorance, know nothing of these things)

 

My 93 is intermittantly over and under charging. The parts store computer said to check for bad ground strap at alternator and also mentioned that a crankshaft sensor, a/c or cruise control problem could be causing this. I did notice that at times when over charging my Tach would act up too. I thought It could be due to excessive voltage but I guess the crank sensor could be shorting at times causing the problem. A/c and cruise are working fine and dont seem to be the culprits. Most of the time it charges fine so I dont believe the alternator is the problem.