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its called the blend door actuator its either stuck or or broken or shorted out it is deep in behind the dash located inside the air box where the heater core is and the ac condenser is its a fun job as for you have to rip your dash apart
The HVAC mode selections on these are controlled by an electric stepper
motor that receives commands from the BCM (body control module). The
BCM decides where the air door should be by looking at where the dash
control input is.
Each mode selected has a different resistance level. From low
resistance to high resistance: Panel, Bi-Level, Floor, Mix and Defrost,
with Defrost as the highest resistance (~100K ohms). A high resistance
or open circuit would probably default the system to defrost no matter
what position the mode control was set to.
If the control is dirty or there is a connection issue, this could
cause this problem. Does playing with the control make any difference?
The BCM can store fault codes with HVAC releated information. The
system can be reset and recalibrated with a battery disconnect, this
will also erase any fault codes.
I would start by looking at the dash mode control.
Open your hood and find a "T" connector right near the battery. Follow the line down below the battery (you will have to get under the Jeep). You will see that the line plugs into a 3 to 4 inch section of 3/16" tubing that is plugged onto a black in color, plastic box. Use a razor knife and trim off about 1/2" of this 3/16" tubing as it commonly cracks where it fits on the nipple of the black plastic box. The vacuum cannot build pressure properly with these cracks in this tubing, and therefore cause the selector door to malfunction when operating heat and a/c. It is a quick and easy five minute fix.