As far as I know the tensioner on the newer V8s cannot be adjusted. They are spring loaded. Even if your belt slips, it wouldn't cut out the blower only the compressor. In other words your blower would blow hot air until the car is restarted or after a few minutes it would restart itself assuming that the engine speed and compressor speed sensor correspond (no slippage).
You either have a bad blower or some kind of bad contact.