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Re: Heater / A-C only blows on windshield (defrost only)
Most all late model vehicles have heater controls that are vacuum controlled. Chances are that you have a vacuum line that has either come loose, or ruptured causing a leak that will not allow the selector flap to move back and forth. If you can acquire a vacuum routing chart (sometimes these are printed on stickers located inside the hood), then routing this particular line and spotting the leak shouldn't be too much of a hassle. If you find out that your heater selector is mechanical, then there is most likely a small plastic clip that has broken causing the mechanical rod that adjusts the flap to came loose. Either way, whether vacuum or mechanical, it sounds like your selector flap isn't moving. That's what I would check first and foremost. Hope this solves your issue. Have a great day!
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. Air won't blow out of the floor or center vents just defrost ? Do you have manual or automatic climate control ? Air Flow Control
Air flow control is accomplished in the following manner:
Primary control is through the function selector knob mounted on the A/C-heater function selector switch, which is part of the integrated control panel.
The function selector knob has the following positions: OFF, MAX A/C, A/C, PANEL, PANEL/FLOOR, FLOOR, FLOOR/DEFROST and DEFROST. The A/C-heater function selector switch combines a vacuum selector valve with an internal electrical switch.
The vacuum selector valve directs source vacuum to various vacuum control motors (18A318). Refer to the Vacuum Control Diagram , System Airflow Schematics and Vacuum Control Chart .
Two internal, single-pole electrical switches are also controlled by the A/C-heater function selector switch. The combination of these electrical switches controls the electrical supply to the A/C clutch and heater blower motor switch (18578).
The position of the function selector knob determines the manner in which the system will operate.
Each position of the function selector knob is detented for positive engagement.
Vacuum Control Motors
The vacuum control motors (18A318):
are located on the A/C evaporator housing, A/C recirculation air duct and heater air plenum chamber (18471).
direct system airflow to the vehicle interior as determined by the remote climate control module or manual override.
The five-passenger seating configuration has an additional vacuum control motor mounted on the heater air plenum chamber to control airflow to the rear seat A/C register (19893).
Usually a sign of a vac leak between the engine and the control on the dash or the blend door. The defrost position is the default when there is a problem with the system so that the windshield stays clear in wintertime.
Common question on this site. On late model cars, the vents are controlled by blend door motors. Small electric motors open and close doors to direct air flow. Chances are you have a blend door that is stuck or a failed motor. The default position is the defrost to make sure the windshield is always clear. Someone will need to look behind the dash to see if all of the doors will move on demand.
Inside the heater box (under the dashboard) there are actuators that are similar to the ones that open your power door locks, they do go bad especially if any water leaks in from a bad heater core or windshield leak.(down the defrost vent grate). Also old age, my truck is a 2000 and I have replaced a couple of actuators.
It will be a cable that will be disconnected. or broken. Youll have to take some of the dash apart to see the cable and follow it to the switch. Dont be affraid to take some things apart and when you cant see, use a mirror to help you see behind the dash. work the control and watch the action. You will fix this dont get frustrated. good luck
Car manufacturers use the defrost mode as a default for safety reasons. Being they want you to be able to defrost the windshield no matter what. So when something goes wrong the system automatically goes to the defrost mode. You most likely don't have the vacuum hose connected under the dash at the climate control assy. Or if this vehicle doesn't use the vacuum hose style you may have not plugged in one of the connectors under the dash or behind the climate control assy. Good luck.
My son's jeep had the same problem. The actuator that controls the the defrost damper came out. Pull the radio out of the dash to gain access to the damper. Looking into the radio hold on the right side you can just see the arm. Move the heater control switch and you can see it moving around. I put a drop of instant glue on the end and pushed back in and its been fine.
the first thing to d is to go under the hood and see if eh cable is stuck if it is not then it has disconnected from its position secondly yu may have a heater control valve which is broken inside which means the water is still flowing nd the heater is on wheher o choose hot ot cold.
the only way t fix the heater control valve is to repace it