Looking at same problem on my JGC, and the forums discuss that it is likely a blend door issue: - gear or shaft slipping
- door motor inoperable
Another possibility is slightly low freon, which may cause better cooling on one side vs. Another, although that seems unlikely it is cheap to check and fix. To repair the blend door requires pulling the dash which is very involved and expensive if done at the dealer. One individual described it as a 700 buck dealer repair. One other slight possibility is that the blend door position requires calibration and below is a procedure posted on a Jeep forum for a Grand Cherokee: I found some info on other Jeep forums and message boards, you might want to try the following calibration test / program.
This may solve your problem. Plus you might want to check your system and see if it is low on R134.
Door calibration function for MTC system as per Chrysler service manual.
1. Turn the ignition to the ON position.
2. Turn the blower motor control to the OFF position.
3. Press and hold the EBL rear window defrost switch down and turn the blower motor control on. Continue to hold the EBL switch down until the EBL (Electronic back light) status indicator begins flashing, then release the mode switch. While the test / function is running the EBL status indicator will flash once per second. If the test / function passes, the EBL status indicator will stop flashing. If the test / function fail, the A/C and EBL status indicators will flash alternately.
I hope this helps, as I intend to go through these same repairs myself.