a/c will not work
 

i have an 83' 300d. when i turn the a/c on. it will not blow cold air and it also will not blow through center vents in the dash. the compressor comes on. i cleaned the diaphram valve on the firewall. this normally was the cause, not this time. i do not think the a/c is being told to turn on and blow through correct vents. is this done by vacuum or from climate control switch?:mad:

Both.

The actual door position for airflow out the center duct requires vacuum application. Since both the defrost door and the center duct are on one command vacuum line a single vacuum failure gives the spring loaded default of no center vent and full defrost.

The decision to place vacuum on that circuit is in the hands of both the pushbutton control unit and the temp control unit (on pre-86 units).