Occasionally when I turn the air or heat on this horrible screaming noise occurs. If I turn the heat/air off for a moment and wait and turn back on I have no problems. But when I apply gas from a stop, it may occur again. If I stop applying gas, it will stop. It’s very loud and scares me and people near me. What is it? I’ve asked a couple of mechanics without success.
It could be the belt is slipping on the air conditioning compressor which slips when warm air and cold air are called for from the dash control panel.