Hoping someone might be able to help me out...Heres the problem....
I have a 96 Dakota 3.9. When the engine is cold, the voltage is low..low enough that when I turn on the headlights and heater, the GEN light comes on...but after the truck warms up, bout 10 miles or so depending on the temp outside (longer if it's colder out) it starts charging and the guage goes back to normal. I want to say its the voltage regulator but it does'nt happen when it' warm outside.
Is the regulator located in the ECM or part of the alternator?
If it is in the ECM, do they make a bypass as to not have to replace the ECM?
Any help or thoughts would be appreciated.....Thanx

 

Most likely just the Alternator. Yes the regulator is in the PCM. Most autopart stores can test the alt for free.

 

Yes...I was going to have it tested but by the time I get to the parts store, it's charging fine. The battery has never went dead (knock on wood) Just dont understand what would cause it not to charge when it's cold...like I said, it charges fine when the weather is warm. Right now it's about 20 - 30 degrees where I live....and at this temp is when the problem started. When the truck warms up though...you can drive all day without a problem....I've never seen anything like it.

 

check also your auto tensioner and belt. The spring inside the tensioner could be getting weak. Usually when tensioners go bad they make a slapping\rattling sound while the truck is idling

 

Or you could just swap out an alternator form the junkyard and see if that solves your problem.

 

Never thought of the tensioner.....I'll check that out and let you know...thanx

 

thats weird. i have a similar problem, but mines completely opposite. charges fine when its cold, but not so fine when its hot. i think mine might be the belt tho...

 

you cannot necessarily trust the test from the auto store. I have a 1993 and the Alternator went bad- it would charge intermittently. When I took it to the local NAPA it happened to be working. later it quit leaving me stranded on the side of the freeway and waiting for the tow truck. This may not be the case with yours- but after I got it home I just replaced the alternator and it has been fine ever since.

good luck!

 

if the alt is fine then it's probably the battery. when a battery is bad and cold it will not take much of a charge, as it warms up it takes more and more charge. have a load test done on your battery, bet it fails.

any chance i can get the name changed to PWC7475, compared to my dakota the mazda sucks!

 

I had an intermittent alternator issue. Temp didn't seem to effect anything. The gauge would drop, and the "check engine" light would come on. Read the code before turning off the truck, and it said "field circuit malfunction". This is when I learned that the alternator is regulated by the PCM. So hoping for the cheaper of two possibilities, I removed the alternator and bench tested it. Tested good. Put it back in and it was charging again. It didn't act up again until I was on my way to Rexburg, ID. On I-15 the light came on again and the gauge dropped. Had the alternator checked again, and tested good again. This time, I decided to replace it just in case. Haven't had a problem since. I'd bet it's the alternator. Temperature can have a big effect on intermittent operation of accessories.