90Iroc

When I turn the heater on, all I get is front defrost no matter what setting I put it on. Even when I tried to put it on A/C. Last summer the A/C worked perfectly. What does this and how do I test parts to see what's bad?
Thanks guys

Brandon

87PontiacBeast

i have the same exact problem.

3gc

Sounds like a vaccum problem not an electrical problem. I was just doing some research on this subject earlier today. I found both of my hvac vacumm lines melted. One of them connects to the intake for engine vaccmm, the other connects to the heater control valve. When the engine vacumm line isn't plugged in defrost is the default. So check to make sure that line is good. It's the purple line on the back on the heater controls.

JamesC

iTrader: (5)

Often the switch, which controls where the vac is applied, leaks. Pull the control out; the switch in question is the one to which the vac harness attaches. If vac is present there, I assume you've found the culprit. Cured my problem anyway.

JamesC