my 98 makes a bee-bee-bee-bee-bee-bee noise from under the dash. It seems to be coming from the heater controls. It happens only when engine is revved to 4000RPM or higher. The noise cannot he heard outside the truck. Sounds kinda like letting the air out of a squeeking balloon. It is not loud.

I am curious if this is a common prob and if anyone knows the fix.

TIA

Chris