I am running 2 amps and 2-10" subs in my truck with the stock alternator. I have my ASP Pulley and my FAL E-fans should be here soon for me to install. At night, just when I am sitting at a stop light my lights dim when the stereo is cranked, when I am driving it is fine. I went to GMC website and supposedly on the 1500 crew cabs, the 145 amp alternator is stock. Anybody know this to be true? I need to look at my original window sticker to make sure. If so, I guess I am needing to go up to a 200 amp unit, correct? I saw a few of these on Ebay. I have already bought the new belts for my asp pulley, if I switch out to a high output alternator, will this change the belts I need or are the pulleys on the alternators the same size?

 

sounds right to have the 145A on your '04 CC. It should be stamped on the case somewhere. I think there are 2 case/frame sizes - the smaller frame alt is the 105A that has been standard for a few years now, the 145A should be a larger frame alt. There is about a 1/2 to 1" difference in belt length with the different frame sizes, but the alt pulley is the same. A decent aftermarket supplier should be bale to give you the correct size alt to match your current setup for belt size.