GMC Repair: airconditioning, gmc sonoma, vacuum leak

Question
My dash vents do not operate at all. The floor blower blows the airconditioning and heat. I can control the heat level but cannot direct heat and airconditioning to dash vents.The truck is a 1992 GMC sonoma V6 it has 119,000 miles on her has been taken care of oil and filters changed every 3000 miles its just like new. HELP PLEASE

Answer
You most likely have a vacuum leak. The A/C controller actually diverts vacuum to vacuum actuators to control where the air blows out of. What you should look for is a vacuum line that goes through the firewall, and see if it has vacuum. If not the trace it toward the engine side until you find the leak. If you have vacuum at the firewall, then take the A/C controller out and see if you have vacuum there, if not then trace it back to the firewall until you find the leak. Lastly if you have vacuun at the contoller, then see if it is diverting the vacuum properly, if so then the actuator is probably leaking, or if not then the controller is bad.

All this said I really think that you will find a vacuun leak in the engine compartment, it is the most usual problem.