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1985 with manual A/C controller. Most of the air is coming out of the defroster regardless of where the controller is set. I have good vacuum at the intake, check valve and everywhere between the there and the firewall. I think my problem is with the vacuum selector inside the controller (the white part pictured below). Can this part be fixed? If so, how, and if not, where can I find a replacement?
The white part GM# 16040637 hasn't been available for a very long time BUT have you actually done the diagnostics in the FSM to sort the actual issue. I believe it's 8A-65-0 for vacuum routing but complete diagnostics will be in that vicinity of the FSM. The valve is '85 - '89 only I believe.
Rodents seem to love the silicone vacuum hoses in that manifold setup. Mine had similar symptoms and the hoses going to the vacuum actuators were chewed. You should be able to use a vacuum tester to verify their integrity from the control head.
The white part GM# 16040637 hasn't been available for a very long time BUT have you actually done the diagnostics in the FSM to sort the actual issue. I believe it's 8A-65-0 for vacuum routing but complete diagnostics will be in that vicinity of the FSM. The valve is '85 - '89 only I believe.
My FSM goes from 7C to 8B, no 8A section. Do you think it could be something other than the switch in the controller?
in my 84, the vent selection slider had become unattached from the rotating wheel that directs the vacuum. that was an easy fix. however in the research for fixingbthat, i read that thete is some sort of greased seal in that rotating wheel that can be a vacuum leak and therefore manifest as defrost only.
1985 A/C Selector Module
