Tmello401

I was driving My 1996 Dodge Ram 2500 12 valve cummins and all of a sudden my gen or (Generator) light when it. It usually means that the aternator is not charging, however the Voltmeter in the truck shows 14.5 volts which is charging and normal when warmed up (Also the Alternator and serentine belt only have 3000 miles on them). Tested both batteries seperatly with a voltmeter and they both said between 13.9-14V. I have an Air-Dog fuel system that was running fine as were all the other electric components. Any thoughts of why the Light went on and how to make it go out would be greatly appreciated....Thanks alot, Tom.

MAC702

I've only seen my GEN light come on once. I was driving through Texas during the ice storm of February 2011. If not for the 10,000# trailer and its brakes, I would not have been able to drive at all. Most cars, and even tow trucks, were in the ditches.

But I was only "idling" and maintaining progress. I was "idling" (under load and moving) for like 12 hours straight. During that time, I started getting my GEN light frequently. I had all the lights on the truck and trailer lit, too.

I can't remember if the blower fan was on or not because it turns out the thermostat was bad, too, and I couldn't get the engine up to temperature to make any heat.

Tmello401

Mine went on during a rainy day last week. My volts dropped to 9 and the light went on. I shut it off then restarted it and it went away. So I believe it was due to moisture and humidity in the engine compartment. Thanks for the reply though

Lil Dog

I've had it happen time to time. I think it has to do with the brushes in the alternator skipping or getting stuck for a second and the computer thinks it can't control the alternator. Like others its happened during wet conditions. Some maintenance on the alternator can help that with taking it off, cleaning the brushes and keeping them lubricated with light electronics lube.

patdaly

FWIW, Mine did this yesterday after plowing thru some drifts ( powdery snow ). Gen light stayed on even though she was charging. Light didn't go off until I shut her off and restarted down the road.

TxDiesel007

had mine go on prior..

truck overcharging, no change with new alternator, wound up being a bad ecm...

MikeR

The brushes on my 95's alternator were worn. So the light started to come on one day, and by day two I could see the charge gauge dropping. Got brushes from the local electrical rebuilder, real cheap and easy to replace.

Yaaintdeadyet

My Gen light went on after I'd removed the alternator to change out the thermostat. Bugged me in that not all the connections were tight. After tightening them all I drove for less than 5 minutes. The Gen light returned yet this time the voltmeter stayed at 12 volts as opposed to the 14 before. I had the Gen bench tested. It passed. Any thoughts?

joem

do these alts have the regulator in them or is it separate?

patdaly

Do a search here on charging system diagnosis. You need to start at the beginning and work you way thru it. PCM is the voltage regulator..