I own a 2007 Dodge Ram 2500 diesel. From the first day I drove it off the lot, it has produced a grinding clunking noise when I turn on the air conditioning after starting the engine for the first time that day. This will happen any time of day, in hot or cold conditions. It will not occur again on subsequent start-ups during the day, almost always on the first start up of the day, and after allowing it to warm up for a few minutes. I can never reproduce this at the dealership, probably because it has already been started once already.

 

Get used to it. It's normal.

 

Sorry Brother its kinda normal. IF someone asks why it does that I tell them I've got so much power that the belt slips and the ALT and A/c compressor can't keep up..