Pretty much as the title says. When I have a change in rpm, either from shifting or from letting off the throttle. Would this be a belt by chance? Weird part is it is only when the fan on.[???]
Having the fan on will cause the load on the alternator to increase, in turn stressing the serp belt and pulleys more. I bet turning the blower motor on high or the high beams on may do the same. Can be very deceiving, though. I've been sure it was one pulley or another before based on where I thought the noise was coming from until I had the belt off and found that another pulley was the one that had a rough bearing.Weird part is it is only when the fan on.