heater and defrost on 1988 silverado

:banghead: My question is concerning the heater and defrost setting on my truck. I've owned this truck for 15 years and have done most of the fix-it work myself, but this one has me stumped. The AC and heater works good when it comes to temprature. The problem is the direction of the air. It doesn't matter what setting you put the control on the air will just blow out the AC vents. The indicator bar on the dash shows it to be on defrost or heater and the air feels hot but the air doesn't blow out of the floor vents or windshield vents. If you have any sugestions please advise me of them. The frost on the windshield in the morning has become a real problem here lately.

Thanks, Mingas

im not sure but i think the mode door is vacuum operated. if so check to make sure that the hose coming from the engine and going inside is not broke or disconnected. otherwise there would be a cable behind the dash that could be disconnected if it is manual.

It is vacum operated and I'll check for any bad vacum hoses. Thanks, Mingas

if you have or have had any clicking doors are electric

w.t.f.are you talking about?

Your HVAC system is electronic, not vacuum. Your problem is not unusual,replacement of the control head (heater control panel) should fix the prob.