Hello, I have a Ford E-150 2003 (4.2L V6 w/ AC). The belt squeals terribly mainly when I put the heater on high, at low RPM and when starting the van. The squealing noise goes away for a bit when I spray belt dressing on the belt.
I replaced the alternator last winter. I've also put a new belt tensioner and both idler pulleys with a new belt about a month ago. The squealing noise stopped for a few days and came back. The only thing I can think of now would be either the AC compressor or the power steering pump? But are any of these affected by the heater? Please I need help it's driving me insane! Thank you so much!