posable heater problem

when i turn on my defrost there is a whering noise that increases as your speed increases and the same when the speed dereases. i have ac and it dosen't do it when it is on. I have a 96 Grand Am GT with the 2.4 leter in it. and sugestions as to the posable problem and solutions.

Thanks

does the sound change with vehicle speed, or the fan speed setting?

it only changes with the the engine speed not the blower fan

Check the voltage going to the fan. The fan may be speeding up when the alternator produces more volts and amps when you accelerate. If the fan motor is going bad it may need the extra voltage and that is why you are hearing it when you speed up. Just a thought.