Archived alternator

[mdlowry]

While driving around today, I had my volt gauge go up to 18V. When I got back, I checked the alternator with a voltmeter. I had 17. 4V off the alternator. I'm now 1400 miles from home on vacation (of course!) and I forgot to bring the service manual with me. This sounds like a regulator problem. Is the regulator seperate from the alternator? Is this a part that I can take care of myself (I have an electronics background)? Part numbers would be appreciated.



Thanks

 

[Shooter]

You did not say what year truck you have. For sure a 24v is regulated by the PCM. It sounds like the alt. is at full field. This could be caused by an internal problem w/ alt. or could be failed PCM.

Try disconnecting the 2 wire plug on the back of the alt. , This is the field leads and should kill alt output. if not then the alt. is internally shorted some where.

The regulation is contoled by the PCM and can only be checked with an OBD2 scanner.

Alt or PCM failures are not very common.



Good luck



EDIT. If you must drive the truck you might try turning on all elctical deviced to load the alt and reduce voltage. We have very high output alt. so it might not work. You might disconnect the field and drive on the batteries. Your batteries are at risk with that high output, they can explode.

 

[mdlowry]

I forgot that signatures were turned off. You are correct that this is a 24v (2000).

 

[mdlowry]

With the PCM unplugged I had no output from the alternator. From what you said, this leads me to the PCM. Dodge wants over $500 for that.



Thanks for the help.



mdlowry

 

[wtrenholm]

The JTEC (PCM) will control voltage in regards to what it sees as system voltage. If it gets an improper voltage input, the output (alt field) will not be controlled correctly. You need a little more diagostics before throwing a controller at the truck. Time for a scan tool.



It seems to have some control to keep voltage at 17. 4 V.



Just my thoughts,

Wayne

 

[MidwestMotorman]

check the cables

I would clean the battery contacts and all wires attached. There could be some resistance in the wiring circuit or at the cables causing the PCM to see lower voltage and thus will cause an increase in regulator output. I would also disconnect both batteries and check them isolated. You could have an impending battery failure of one of them causing a system draw. I would check that before the top of a battery explodes into the hood. You might also want to let the batteries sit disconnected for a day and then check their voltage again to find the battery with a possible draw or short.



Good luck.

 

[mdlowry]

Well, I checked everthing I could, and ended up having the alt checked also. The alt was good, and also the batteries. It was the regulator circuit that had failed. I had forgot to mention in the first post, that it wasn't a constant 18v, but started at battery voltage and went up and sometimes varied.

I had talked to one of the Dodge dealers in the area, and they didn't have the part. The nearest one would have taken 3-4 days to arrive.

When I was in the alternator shop having it checked, they said they could put an old external regulator in for about $70 (as compared to the $600+ Dodge wanted for the module). I felt that was the best way to go at least for now. I got it repaired for less than $75 (inc tax) in a couple of hours and I'm now home.

Thanks to everyone for the help!

mdlowry

 

[MidwestMotorman]

interesting fix

Can you tell us what procedures they did to install the old style? Can you give us any info on what year of components they used and the rewiring process? You never know when a fix like that will have to be done 1500 miles from home.

 

[mdlowry]

I'll get it up soon. I'll have some time in the next couple of days so I'll take a look and get it posted.

mdlowry

 

[mdlowry]

It's up in the 24valve non-engine section.

http://216.235.147.117/forums/showthread.php?s=&postid=359863#post359863