The heat and A/C will only blow out the floor and windshield vents but not the forward facing vents. What do I need to replace to fix this issue?
My car has 51000 miles.
My car has an automatic transmission.
It's not possible for me to tell you what exactly has failed on your car. I can however set you down the right path.
There are three components at work here. The mode switch that you turn on the dash, the mode door actuator that is mounted under the dash and the mode door itself. The most common failure for this system is the mode door actuator followed by the mode switch.
You will need to do some Googling to locate the actuator, but I would get to the actuator and tap on it. Often times this will free up a frozen actuator. If once you tap on it, it begins to move, I would begin by replacing the actuator. If the actuator is very difficult to replace, I would make sure this test is repeatable to be sure you haven't missed something else. Check the connector, it could have a bad connection.
To do some testing at the mode switch, you will need a wiring diagram and remove the mode switch. With a test light, make sure you have power and ground at the appropriate terminals at the correct time. You can also do some trouble shooting that can help you diagnose the mode actuator. Often times accessing the mode switch first can be easier do to the hard to access nature of the actuator.
Lastly, if both those seem to be working, I have seen the mode door itself have problems. If you remove the mode actuator, you should be able to manually move the mode door to test its operation. If it binds or the the air isn't directed out the correct vents when you move it around, you will need to remove the heater box and disassemble it to see what has failed at the door.
If you feel like you need assistance with these checks, enlist a qualified mechanic who can accurately diagnose this issue with your A/C and fix it accordingly.
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