steverr

When I put the defroster on there is a hissing noise coming from the dashboard, it only comes on if just the defroster is on, if i put it on the mode where heat goes to feet and defroster it doesnt do it. If i use regular heat it also doesnt do it..any one know why it would make a hissing noise

WhiteFormula98

iTrader: (10)

Did you check to see if there is a snake in the vicinity?

SparkyJJO

iTrader: (11)

Could be a vacuum leak, I'm pretty sure the system that directs the airflow is controlled by vacuum lines and valves.

sway99bird

iTrader: (22)

It's a snake

ghardester

The control for the heat/air/defrost is controlled by vacuum. There is a multi hose fitting behind the dial. Pop off the trim and remove a couple screws and pull out the control. You may have a leak behind the control.

steverr

but how come I only hear it when the defroster is on, and not the heat?