Heater Performance Test: Notes
WARNING: This page is about a different car, the 2007 Jeep Grand Cherokee. However, it is still accessible from the selected car via links, so may be relevant.
Before performing the following tests, refer to COOLING for the procedures to check the engine coolant level and flow, engine coolant reserve/recovery system operation, accessory drive belt condition and tension, radiator air flow and the fan drive operation. Perform the A/C System Performance Test, which is found within the HVAC System Test (refer to 24 - HVAC Electrical Diagnostics). If any diagnostic trouble codes (DTCs) are found in the A/C-heater control or the powertrain control module (PCM), repair as necessary.