not sure why but i always hear the ac hissing and blowing, and i've oly gotten it to go off by having the defrost on for about 20 mins then turning it all off, anyone know why or how to fix it?

 

Sounds like the problem I had .There is a round valve with vacuam hoses hooked to it on the back of your heater control that goes bad and lets vacum escape and makes it make that hissing noise it has different colored hoses hooked to it so make sure you hook them back up right. The part you can get from autozone or napa I think its called a heater control valve. hope this helps it fixed mine. Check the hoses to to make sure they have no holes in them.

 

If the controls only function on defrost, there's a vac leak, often, as Rich mentions, at the control head. Stick an ear to the pass side of it for verification. The part is shown below:

https://www.thirdgen.org/forums/atta...duct010707.jpg

JamesC

 

thanks guys, i always get great info from this site