I have a 92 camaro with a 305, and I am having problems with the heater, it blows cold air when the vacuum line is connected to the heater control valve, but when i disconnect the vacuum line the heater works really good and blows hot air. I replaced the heater control valve but I am having the same problem. Does anyone know how to fix this? Is driving around without the vacuum line connected gonna cause any problems? thanks

 

sounds like the hoses are connected wrong. vacuum should controll the flow of coolant through the valve.

 

i just checked the hoses and they are connected right. Could there be anything else? The vacuum line has a vacuum also. Thanks for your help

 

wrong style of valve... pressure vs vacuum operated one?

 

im having the same prob in mine and i switched out the heater control valve and still the same prob. just out of curiousity, is the air also only blowing out of the defrost? and is the hvac making a hissing sound when you switch it from cool to heat? also i did see where the heater control valve vacuum line goes connected in to the block, could it be that part that has gone bad? the funny thing is i just had a swap done not to long ago, and the mechanic said he may have bypassed the heater core. So im pretty sure if someone can explain this by pass procedure we might be fine, but if thats what your gonna do with your vaccuum line, just put a plug on the end to be safe.