Air blower problem

Hello everyone, I have seen many problems here similar or the same. I have a 1999 Chevy Astro van, My Air was not blowing out of the vents so my brother and I had to take off the dog house and replace the hose and reconnect it to a unit under the hood, well the air was working and I was on my way home I heard a hissing sound from under the engine. Now we've been looking for a leaky or loose valve somewhere for 2 days and can't seem to find it, my other brother says it may be coming from the injectors but I didn't have this problem before we reconnected the hose. My Service engine light has been on for a little over a month now and my van idles a little rough. Any help would be appreciated.

Thanks Cal

The vacuum line for the HVAC system connects to a fitting on the drivers side rocker arm cover along with a larger line for the PCV valve. The smaller line crosses over the top of the engine and connects to a tee near the evaporator housing. The line is about 1/8" in diameter and made of black plastic. The plastic dries out, gets brittle and breaks. When it breaks, all air flow defaults to defrost. Connect a piece of rubber hose over each end of the broken line to "splice" it back together. Eliminate as much of the old plastic line as possible.

As for the hissing sound, a good visual inspection should find the problem. If not, try a fine spray of carb cleaner, (they usually come with a red plastic nozzle extension taped to the can) directed around the top of the engine, especially along the intake manifold, and listen for a change in idle quality and engine RPM. Another trick is to take a piece of 3/4" heater hose and hold one end to your ear while moving the other end around searching for leaks while the engine is idling. When you get the hose close to the leak, you can hear it loud and clear! This will help in pinpointing the leak. Sounds "shade tree" but it works every time. Hope this helps.

Thanks, i was about to post this problem too as i can hear the vaccuum leaking, but couldn't find it as none of myvalves are working to blow it to either air vent or windshield etc..., now i have a better idea where it might leak.

Cheers