I am helping a good friend with his 97 3500 dually auto ex cab 4x4. When the truck is at an axle the charge voltage is 13.79. If I turn on the lights wipers and the defrost the charge voltage will drop slowly down to 12.35 volts. Also the Alternator gets very hot. I was using a temp gun and the engine was only 105 degrees and the alt was 220 degrees. I smell the alt like it is burning I am pretty sure that the alt is bad but thought I would ask and see what you guys think.

 

What do you mean, "when the truck is at an axle"?

I'm thinking that's too hot for the alternator, and 13.79 is kinda low, let alone 12.35. I'd want to see 14.2 - 14.5 volts. But as to whether the problem is the alternator or something else, I'm not sure. Why don't you remove the alt. and take it to NAPA for a free alternator check?

 

Sorry I meant idle not axle. I think I got it figured out. I hooked up my scanner and the desired charge voltage is 13.8 and it will charge that much with no accessories on. But when the lights and defroster are on the charge drops to 12.00 and the desired charge voltage is still 13.8. So I am sure the alt is bad.

 

I replaced the alt tonight and so far it is fixed.