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Symptom Troubleshooting Index

SYMPTOM TROUBLESHOOTING CHART

Symptom Diagnostic procedure Also check for
The blower and heater controls and the A/C system do not work
The A/C compressor clutch and the A/C condenser/radiator fans are inoperative, but the blower and heater controls work
The A/C compressor clutch does not engage, but the A/C condenser/radiator fans operate, and the blower and heater controls work
The A/C condenser and radiator fans do not run at low speed with the A/C on, but the blower and heater controls work normally
The A/C condenser fan does not run at high speed, but the radiator fan does. Both fans run at low speed
The condenser/radiator fans do not run at high speed, but both fans run at low speed
The condenser/radiator fans run always at high speed (never at low speed) with the A/C on
The A/C compressor clutch cycles rapidly on and off
Warm air comes out of the vents, and the high pressure liquid line is very hot
  • Probable causes: The A/C system is overcharged (too much refrigerant), or the condenser is malfunctioning
  • Recover A/C refrigerant (see REFRIGERANT RECOVERY ), then check the condenser for restrictions or poor airflow. Repair as needed. Recharge the system to specifications (see SYSTEM CHARGING )
  • Incorrect tension or abnormal wear on the drive belt. Replace the belt and/or the belt tensioner as needed.
  • Proper operation of the condenser/radiator fans. Repair as needed.
  • Signs of an overheated engine. Repair as needed.
Warm air comes out of the vents. The suction line is cool to warm, and the discharge line is warm to hot
  • Probable cause: A/C system is low on refrigerant, indicating a possible leak
  • Do the Refrigerant Leak Test (see REFRIGERANT LEAK CHECK ), and repair any leaks. Recharge the system to specifications (see SYSTEM CHARGING )
Warm air comes out of the vents. The suction line is cool to warm, the discharge line is warm to hot, and there is no frost on the expansion valve
Warm air comes out of the vents. The liquid line or the condenser outlet is abnormally cool, or there is frost or condensation on the receiver/dryer
  • Probable cause: A restriction in the high-pressure side of the system
  • Recover A/C refrigerant (see REFRIGERANT RECOVERY ), then check the liquid line, the receiver/dryer and the condenser for restrictions. Repair as needed. Recharge the system to specifications (see SYSTEM CHARGING )
 HVAC DTCs (see GENERAL TROUBLESHOOTING INFORMATION )
There is heavy frost or condensation on the expansion valve, and frost on the suction line
  • Probable cause: A restriction in the low-pressure side of the system
  • Recover A/C refrigerant (see REFRIGERANT RECOVERY ), then check the suction line and the expansion valve for restrictions. Repair as needed. Recharge the system to specifications (see SYSTEM CHARGING )
 HVAC DTCs (see GENERAL TROUBLESHOOTING INFORMATION )
Warm air comes out of the vents, and there is frost on the expansion valve
  • HVAC DTCs (see GENERAL TROUBLESHOOTING INFORMATION )
  • Check the old expansion valve for contamination. If contaminants are found, replace the A/C system component that caused the contamination.
The temperature of the liquid line is the same on both sides of the expansion valve, and the evaporator coil or suction line has heavy condensation
  • HVAC DTCs (see GENERAL TROUBLESHOOTING INFORMATION )
  • Check the old expansion valve for contamination. If contaminants are found, replace the A/C system component that caused the contamination.
Warm air comes out of the vents, but operation is normal otherwise
Driver's and passenger's side vent temperatures vary by more than 20 °F (11°C)
  1. Probable causes: The recirculation control door or the air mix door is malfunctioning
  2. Do the following troubleshooting:
Insufficient heating
  1. Check the coolant level (see COOLANT CHECK )
  2. Check the radiator cap (see RADIATOR CAP TEST )
  3. Check the coolant temperature during normal operation
  4. 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
  5. Do the Air Mix Control Motor Test (see AIR MIX CONTROL MOTOR TEST )
  6. Check the blower motor unit for obstructions
  7. Check for air leaks around the ducts and vents
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