Blower air just through defroster vents, not front vents

coolant fan relay diagram

i hadsimale problems on my taho the ac wul not blow cold n the back only the heater would blow and the front would not blow i had to chang the front blower motor and the blower motoer relay in the back every thing is on the top of the rt pass wheel hump swap them out there the same parts to see what broke hat stuf is expencive hope this helps

You have a loss of vacuum from the engine, first check under the hood and make sure the vacuum storage tank is not damaged and leaking and it has vacuum in it when the engine is running. If all that is ok then move on to the line that goes inside the truck and verify it has vacuum.

I think your problem is the head unit that selects where the air comes out ie. Face, floor, defrost, or hi-level face and floor. If that's not working then it will not let you switch location that you want the air to come out.

the blower motor is under the hood on the pass side. u have to remove the wiper and radiator bottles and also the head light. than take out the 7 bolts that hold the blower motor in than u have to remove the squirel cage before the motor will come out. or it could be the Blower Motor Resistor.

It is the vent control. It is located on the passenger side behind the dash. It is vacuum controlled. It can fail and not let you change the vent positions.

Good Luck!

If there is no vacuum to the mode door control motor theheater/A/C system will default to "Defrost" If there is no air coming out the vents or floor - check to see if you have air blowing out the defrost vents. If there is air coming out the defrost, then the most likely cause of your problem is a broken or disconnected vacuum line that feeds the mode control switch. On your vehicle, the vacuum supply line connects to the brake booster hose under the hood. there is a check-valve on the line between the firewall and the brake booster that can fail and leak vacuum. if there is no problem with the vacuum supply line under the hood, then the most likely cause is a bad mode control switch. (switch leaking vacuum)

If there is no air coming out the defrost vents, but you can hear the blower motor running, there is most likely a resriction of airflow etween the blower motor and the air outlet plenum. I have seen A/C evaporators completely cloggedup that will not pass any air. I have also seen paers and napkins that have gotten sucked out of the glovebox area and into the "Recirc" air inlet. Another thing I have seen several times is nests made by mice or other small rodents in the blower motor housing.

had this trouble in a dakota it was a blend door in the heater unit. had to remove entire dash to repair

remove the plate under the dash and see if the hoses are fitted to the vents you will need to do n/s and o/s

have the water pump checked out, i had a van that did the same thing and founf i had a bad water pump it fixed the problem.also check the blower motor to make sure its working right by tapping on it while you have the car running. the car will survive dont worry its going to be one of those two things im pretty sure.