I have a 96 gmc sonoma with 189k miles, and the swith contorl for the heater and ac goes on but it only blows out of the defrosters and floorboards. Both the heat and a/c work fine but the controls do not change where the vents blow out of. Thanks for the help.
It sounds like you lost a vacuum hose under the dash somewhere. The vacuum controls the mechanism that controls the air flow selection.
You might be able to here the vacuum.
And if you; 're a smoker, blow smoke under the dash and follow it.
Or bad control valve
June, 25, 2007 AT 12:31 PM
I'll try that, thanks for the help, I hope it works, its kind of annoying.