When i turn the A/c on the air shoots out the defrost vents for a while. After I get the truck running for about 5 minutes it would go back to normal and shoot the air out the vents. Sometimes when I am accelerating the a/c will switch to defrost mode and then go back to coming out the vents normally when I would slow down. Also there is a hissing sound coming out from behind the glove compartment sometimes. The hissing sound sounds like something is leaking or rubbing, but i'm not sure? Can anybody point he in the direction of finding out what is wrong with my a/c system. I live in texas and am going to school in Waco. It is still very hot down here so any help would be appreciated.

 

sounds like a vacuum leak, you will have to look at the vacuum lines

 

I'm having a similar problem. When I put my ac on max it switches to defrost. When it's on auto it will run for a while ok then switch to defrost. The only time it works properly is when it's set on panel/floor but it's not cooling well in this mode. The blower speed in all these modes seems to speed up and slow down at will. Could this be a problem with the climate control sensor or another electronic part going bad?

Thanks guys/gals!

 

I was also thinking vacuum leak.

by the way, where do you go to school in Waco?

-Mike