Without Climate Control

Driver's and passenger's side vent temperatures vary by more than 20 °F (11 °C)

Probable causes: The recirculation control door or the air mix door is malfunctioning

Do the following troubleshooting:

Recirculation control motor circuit troubleshooting Recirculation Control Motor Circuit Troubleshooting

Air mix control motor test Air Mix Control Motor Test

Also check for

HVAC DTCs How to Troubleshoot the Heating and A/C Systems (Without Climate Control)

Also check for

Poor or loose connections at the terminals