i have a 89 f150 that I am getting low air flow from the heater no matter what setting I have it on it hardly blows out the vents. I have had the dash off all the vents out and cleaned nothing blocking the air flow I just don't know where it is going. the fan works fine I pulled the heater core to see if that was plugged and blocking the air flow I cleaned that up good I pulled the evaporator for the AC off cause it seemed like that was blocking the air but still didn't do anything. I even pulled off on top where the outside air comes in and cleaned that out. I am at a loss this truck is my daily driver and not having heat is getting really old any ideas would be helpfull