somebody i know has a 2004 2500hd with a 6.0. it is pretty much stock with a 105amp alt. he is going to put electric fans on so he put a 145 amp delco on. this is the second one because they quit charging after 3000 rpms. the 105 does perfect but the damn 145s dont work. does something need to be changed. what if the belt is to tight would that have anything to do with it?

 

Is it possible that the PCM needs to be retuned for the new alternator? If I remember correctly, there's a circuit in the newer PCM's (not 99-00 that's for sure), that duty-cycles the field coil.

When I installed a 145amp alt in my 99, which has an 02 PCM, It worked, but I (as did many others), got a flashing battery lt. I had to run a wire from the plug in the alt to a pin in the PCM. Different scenario than yours...just an example

Oh yea, almost forgot, there's a belt for a Denali that I used when I installed mine...part #12576451. Not sure if it's the same one that'll work on your truck though. Gotta figure that having a real tight belt on there can't be doing anything good for the bearings of the accessories.

 

i thought on an 04 you could plug the 145 in and it would work?

 

I had a 200 amp alt built for my truck and ended up having to change regulators on it...the original one was turned on and off by the PCM, and when I got up in RPM's it would shut the alt off. The new one keeps the alt charging all the time. The only problem after that was the battery light was on all the time. Had that fixed with my PCMFORLESS tune. Not sure if it's the same with the factory GM parts, but something to look into.

 

Actually that's what I thought too...hopefully someone has a service manual with the circuit description that can chime in...