I have a question about my 1987 1/2 ton 4x4. The problem is with the ventilation system. The switch works to change the speed of the fan, and I can also adjust the temperature. The problem is that I can't control which duct the air comes from. When I turn on the heater/AC, the air comes from every vent at once. This makes defrosting especially time consuming. I am told that there is a valve that controls this, but I am unsure if its location. Please help if you can. Cody Pelfery
I have a 76 blazer which I believe has the same basic design of the 87 dash / parts .. when I pulled my heater control to change the switch out for the heater, I noticed that there is a cluster of vacumn lines hooked onto the heater control which I think controls the position of the vents. I would check those vacumn lines ( if you have them) and make sure you have vacumn, etc..... hope this helps . eugene 1968 chevy 1969 gmc 1976 blazer 1992 gmc 4x4 1995 monte carlo
I checked that, and everything seemed to be intact. I did not take the hoses off to check for vacuum, but I did make sure they were all hooked up.
