Engine/Transmission (1994 - 1998) Alternator not charging

[MatthewPark]

I have been having an intermittent problem with my alternator and getting code 41, "An open or shorted condition detected in the alternator field control circuit. " Yesterday the CE light came on, and about 30 miles later, the alternator stopped working. This has happened twice before, I had the alternator tested and it's fine, and the problem randomly fixes itself.



The fuse is good. The connections are clean and good.



What post on the battery do I add voltage to to excite the alternator?



I'm about to throw a 1 wire GM alternator on. I can't have a truck with a charging system that acts like this and is difficult to diagnose by means other than throwing tons of money at it.

 

[ndurbin]

I had my truck throw this code, called and talked to the dealer about it and had the alt. bench tested off the truck. Dealer said the only fix for that is to replace alt. Weird thing was my alt. tested fine off the truck but wouldn't charge on the truck. So I bought a new alt. and put it on, now it charges just fine. It's kind off a stupid set-up anyway, alt. gets it's signal from the PCM. Which if the regulator in the PCM goes your really SOL.



But I picked up an alt. for $180 with a lifetime warranty.



Nathan

 

[PUMPERDUDE]

I had the same code. It started as an intermittent problem. First started when towing... Stopped at an Autozone for a free check. The salesman said it was putting out about 65% of what it should. Put in a new altenator... problem gone. Lifetime warranty I inspected the core before I returned it for credit... It was toast. If yours is the original it might be as well. Good luck with it.

 

[Jeff H]

Oh great way to go. My 95 has 220k. The de-arn alt make interesting noises when its moist outside.

 

[crabman]

Matthew,

Without a DRB it is very difficult to diagnose electrical charging problems. If you can borrow one or know someone who has one who will help, you can find/fix the problem. Go to Techauthority and purchase their "Powertrain Diagnostic Procedures" service manual. I have one for 94-95 5. 9L Cummins Diesel Truck but without a DRB you can not run the tests.



You can check wiring between the alt. field driver(DG) and the powertrain control module. PCM pin #20

PCM pin #57 DG/OR is the other small connection on back of alt. which is DB.

Be sure to disconnect both batteries and take out 120 amp. fuse before doing con. check.

Good Luck

crabman

 

[MatthewPark]

Thanks for all the replies, I will dig into this thing as soon as the problem RE-APPEARS, because 10 miles into my first drive yesterday, the problem disappeared, and I can't get the symptoms to come back.

 

[crabman]

Mine Also

Matthew,

Mine has done the same thing, check my thread on "Electrical Gremlins" . Drove me crazy :{ but then, it fixed itself(?) and has been good ever since .

I really love electrical problems :-{} .

Good Luck!

crabman