On my 81 Malibu there is a hissing noise coming from the HVAC head unit. It goes away if I tap on it. Sometimes it’ll change the air flow to where I select and sometimes I have to direct it a few times. Is it that vacuum switch?? Or any other advice is appreciated!!! Thanks!!!
Hissing coming from HVAC head
- Thread starter Toolman78
- Start date
Vacuum leak. Engine vacuum drives the flappers in the ductwork. Pull the radio plate and look for cracked hoses or head unit nipples. Be gentle. The lighter plug comes off by pinching the plug on both sides.
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