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Climate Control System Symptom Troubleshooting Index

NOTE:

For cooling fans control, review the Cooling Fan Controls System Description .
For cooling fans high/low switching A/C refrigerant pressure, review the A/C Pressure Sensor in the A/C System Description - Refer to: A/C System Description - Components .

Symptom	Diagnostic procedure	Also check for
The blower, the heater controls, and the A/C system do not work	Symptom troubleshooting - Refer to: Climate Control System Symptom Troubleshooting - The blower, the heater controls, and the A/C system do not work	Climate control DTCs - Refer to: How to Troubleshoot the Climate Control System Blown fuse No. C36 Poor ground at G405 Climate control unit Harness/connections
The A/C compressor clutch and the A/C condenser/radiator fans are inoperative, but the blower and heater controls work	Probable cause: A/C pressure sensor circuit malfunction or evaporator temperature sensor circuit malfunction Troubleshoot the A/C pressure sensor circuit: A/C pressure sensor circuit low voltage A/C pressure sensor circuit high voltage NOTE: The A/C pressure sensor circuit can malfunction without setting a DTC	Climate control DTCs - Refer to: How to Troubleshoot the Climate Control System PGM-FI DTCs Abnormal A/C system pressures - Refer to: A/C System Test Evaporator temperature sensor Harness/connections
The A/C compressor clutch does not engage, but the A/C condenser/radiator fans operate, and the blower and heater controls work	Symptom troubleshooting - Refer to: Climate Control System Symptom Troubleshooting - The A/C compressor clutch does not engage, but the A/C condenser/radiator fans operate, and the blower and heater controls work	Climate control DTCs - Refer to: How to Troubleshoot the Climate Control System PGM-FI DTCs Power distribution module DTCs - Refer to: How to Troubleshoot the Body Electrical (2022 - 2023) or How to Troubleshoot the Body Electrical (2019 - 2021) Blown fuse No. Af A/C compressor clutch Climate control unit Power distribution module PCM Abnormal A/C system pressures - Refer to: A/C System Test Harness/connections
The A/C condenser/radiator fans do not run at low speed with the A/C on, but the blower and heater controls work normally	Symptom troubleshooting - Refer to: Climate Control System Symptom Troubleshooting - The A/C compressor clutch does not engage, but the A/C condenser/radiator fans operate, and the blower and heater controls work	Climate control DTCs - Refer to: How to Troubleshoot the Climate Control System PGM-FI DTCs Blown fuse No. B16 Poor ground at G301 Radiator fan relay Fan control relay Radiator fan motor A/C condenser fan motor PCM Harness/connections
The A/C condenser/radiator fans do not run at high speed, but do run at low speed with the A/C on	Probable cause: Malfunction in the fan(s) high speed circuit Do the following troubleshooting as needed: Do the symptom troubleshooting - Refer to: Climate Control System Symptom Troubleshooting - The A/C condenser/radiator fans do not run at high speed, but do run at low speed with the A/C on Radiator fan high speed circuit troubleshooting	Climate control DTCs - Refer to: How to Troubleshoot the Climate Control System PGM-FI DTCs A/C condenser fan relay PCM Harness/connections

*: With rear temperature control

Symptom	Diagnostic procedure	Also check for
The blower fan runs slower than expected in cold weather (when in AUTO mode) NOTE: It is normal for the blower fan to run slowly until the coolant temperature rises when in AUTO mode	Probable cause: Engine coolant temperature (ECT) circuit malfunction Troubleshoot the ECT sensor circuit: ECT sensor 1 circuit low voltage ECT sensor 1 circuit high voltage ECT sensor 1 circuit range/performance problem	Climate control DTCs - Refer to: How to Troubleshoot the Climate Control System PGM-FI DTCs Manual blower motor operation
The A/C compressor clutch does not disengage when the A/C switch is off	Probable cause: The A/C compressor clutch circuit is on (energized) continuously, shorted to ground, or the A/C compressor clutch is mechanically jammed Do the symptom troubleshooting - Refer to: Climate Control System Symptom Troubleshooting - The A/C compressor clutch does not engage, but the A/C condenser/radiator fans operate, and the blower and heater controls work , and repair any circuit problems If the A/C compressor clutch circuit is OK, then do the A/C compressor clutch check , and repair any problems with the A/C compressor clutch	The A/C compressor relief valve. If it has vented refrigerant to the atmosphere, correct the problem with the A/C compressor clutch or clutch circuit, then replace the A/C compressor relief valve
The A/C compressor relief valve has vented refrigerant NOTE: This indicates the A/C system high side pressure was high	Probable cause: A high-side restriction, the A/C condenser/radiator fans are inoperative, or the A/C compressor clutch is not disengaging If the fans and A/C compressor clutch operate normally, feel the lines for restrictions Do the A/C system contamination inspection - Refer to: A/C System Contamination Inspection If the A/C compressor clutch will not disengage, do the symptom troubleshooting - Refer to: Climate Control System Symptom Troubleshooting - The A/C compressor clutch does not engage, but the A/C condenser/radiator fans operate, and the blower and heater controls work If the fans are inoperative, do the symptom troubleshooting - Refer to: Climate Control System Symptom Troubleshooting - The A/C condenser/radiator fans do not run at low speed with the A/C on, but the blower and heater controls work normally	PGM-FI DTCs
Driver's and passenger's side vent temperatures vary by more than 20 deg.F (11 deg.C)	Probable causes: The air mix doors are malfunctioning Do the following troubleshooting: Driver's air mix control motor test Passenger's air mix control motor test Low refrigerant charge A/C compressor variable capacity control solenoid malfunction Do the A/C compressor variable capacity control solenoid test	Climate control DTCs - Refer to: How to Troubleshoot the Climate Control System Harness/connections
HDS does not communicate with the climate control unit or the vehicle	Troubleshoot the DLC circuit - Refer to: DLC Circuit Troubleshooting (2019 - 2021) or DLC Circuit Troubleshooting (2022 - 2023)
Insufficient heating	Check the coolant level - Refer to: Coolant Check Check the radiator cap Check the engine coolant temperature (ECT) during normal operation with the HDS Check the heater core inlet hose temperature: If it is COLD, check for restrictions in the hose, a damaged or leaking thermostat, or a damaged or leaking water pump If it is HOT, check for restrictions in the heater core. Back flush or replace the heater core Check the operation of the air mix doors: Driver's air mix control motor test Passenger's air mix control motor test Rear air mix control motor test* Check the blower motor unit for obstructions Check for air leaks around the ducts and vents	Climate control DTCs - Refer to: How to Troubleshoot the Climate Control System

*: With rear temperature control