Climate Control System Symptom Troubleshooting Index

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Symptom	Diagnostic procedure	Also check for
The blower and heater controls and the A/C system do not work	Symptom troubleshooting	Blown fuse No. C36 (10 A) in the under-dash fuse/relay box Poor ground at G406 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 PGM-FI DTCs Abnormal A/C system pressures 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	Climate control DTCs PGM-FI DTCs Power distribution module DTCs Blown fuse No. Ab (70 A) in the 12 volt battery terminal fuse box A/C compressor clutch Climate control unit Power distribution module PCM Abnormal A/C system pressures 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	Climate control DTCs PGM-FI DTCs Blown fuse No. B10 (30 A) in the under-hood fuse/relay box Poor ground at G202 A/C condenser fan relay Fan control relay A/C condenser fan motor Radiator fan motor PCM Harness/connections
The A/C condenser/radiator fans do not run at high speed, but do run at low speed	Probable cause: Malfunction in the fan(s) high speed circuit Do the following troubleshooting as needed: Do the symptom troubleshooting Radiator fan high speed circuit troubleshooting	Climate control DTCs PGM-FI DTCs Poor ground at G204 Fan control relay PCM Harness/connections

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 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, stuck A/C compressor clutch relay, or the A/C compressor clutch is mechanically jammed Do the symptom troubleshooting , 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 If the A/C compressor clutch will not disengage, do the symptom troubleshooting , and check for mechanical problems If the fans are inoperative, do the symptom troubleshooting	PGM-FI DTCs
Driver's and passenger's side vent temperatures vary by more than 20°F (11°C)	Probable causes: The air mix doors are malfunctioning Do the following troubleshooting: - Air mix control motor test - Passenger's air mix control motor test Probable causes: Low refrigerant charge	Climate control DTCs Harness/connections
HDS does not communicate with the climate control unit or the vehicle	Troubleshoot the DLC circuit
Insufficient heating	Check the coolant level Check the radiator cap Check the coolant temperature during normal operation 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: 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