Air conditioning control panel button not working on 1996 chevy truck . The control knob for the defrost/ dash vent/ floor is only working in the floor position . I checked the 10 amp AC fuse under the hood and is good . AC is not blowing any cold air .Any help would be greatly appreciated..... thank you

SOURCE: air conditioning on a 2000 chevy impala

If it will not switch to any different positions,and you did not have this problem prior to repair.Check for a leaking vacuum line to the control unit.The line should run through the firewall to the control unit.Good Luck!!!

SOURCE: 2004 Chevrolet Silverado vent control

sounds like the vacum lines thats hooked up to it is disconnected check that first

SOURCE: heater control 98 chevy s10 blazer

These trucks have a problem where moisture builds up in the heater box then freezes. When this freezes and you change your heater settings it breaks the shaft for the blend door. If this is what happened you should be able to look under the dash above and to the right of the gas pedal and you will see two vaccuum accuators one of them you should be able to wiggle around the linkage if it is broke. To fix this you need to remove the entire dash to get the heater box out which involves discharging the AC and draining the coolant because the heater core and evaporator come out. Please rate.

SOURCE: 1998 Mustang - AC blows only through Defrost vents

You probably have a vacuum leak on the passenger side. its a small plastic hose some times they come unpluged from the engine. or brake.

SOURCE: PROBLEM WHEN SELECTING THE DIRECTION FOR THE AIR

Sounds like you have a supply vacuum problem. When you lose supply vacuum to the control head it defaults to defrost.