I have a 1989 Chevy K1500 with a/c and I get almost no heat from it. I’ve pulled out the glove box and there are no cables to be found to adjust. It seems that there are motors that run everything, but I fear pulling the dash apart without knowing where to go. The only motor that seems to be in full display makes an odd running noise when switching from hot to cold and pushing on it when switching it quiets it, but I’m not sure if that’s the issue. Have you heard of anything like this??? Sometime I even feel cold air against my leg when driving and the setting on defrost or dash. That leads me to think of a open vent door. Coolant is full, thermostat, waterpump are new and the engine runs at perfect temp.
That is likely to be the issue. Do you know if those motors are vacuum or eclectic?In your opinion is the odd sound made by motor you mentioned something new? If so motor could be going bad; or worse, I hate to say it, if the motor operates the blend air door- the door that moves when you go from hot to cold, that door could be broken: plastic door as it moves goes against a strong “wind” inside heater/ac housing, eventually 1 of the 2 plastic “studs” that are part of the door and fit into
holes in heater/ac housing (“studs” pivot in these holes)- 1 of these “studs” can break, causing door to cock and partially jam, making motor work harder, creating odd sound. See if you can CAREFULLY remove motor to eyeball door and ANYTHING ELSE. If you don’t find anything see if you can remove items attached to heater/ac housing w/ the goal of looking inside housing to see ANYTHING wrong (most likely broken
door but it might not be blend door)- before you remove housing. Usually, if there’s vacuum motor(s) operating some door(s) and vac hose falls off so no vac source; heat/ac system will go automatically to defrost instead of floor- (your scenario; blowing on your leg). Still, get under dash and ceck for ANY vac hoses disconnected, then do same under hood for any vac hoses coming from heater/ac housing- unless you’re sure vac plays no part in heat/ac op.
Thermostat maybe stuck open.