I just got my Blazer, my dad changed the AC compressor before I got it (bought it in OH and drove it down to AL) but I notice a slight hissing sound behind the AC controls when I turn the AC on. Probably a vacuum leak? Or would it be a coolant leak? I don't notice the brake booster losing vacuum, seem to be working fine. Any info would be great, THANKS!

 

lol..I have the same issue. there are several vacuum Diaphragms behind the dash that could be leaking. the control panel on the dash has several vacuum lines going to it and could be loose. They all connect to the same area behind the panel and there is a second joint futher inline. I plan on removing mine this weekend and using a mighty vac hand pump to test the lines for leaks. hopefully i will find that I loosened the fittings when I installed my Radio last summer.

 

If I don't get to fixing it anytime soon, what will it hurt? Just continue to get worse and eventually rob vacuum from the rest of the car?

 

It would be nice if everyone remembered to include all the extra stuff.. like what year and model and, in this case, manual or automatic climate control.
~Not that it really matters or anything.~

I dont mind doing research on solutions to a problems.. it's good for brain cells.. but it pisses me off when I have to search to see if the person asking for help on a problem mentioned the pertinent facts somewhere else.