Heater Performance Test

WARNING: REVIEW SAFETY PRECAUTIONS AND WARNINGS IN THIS GROUP BEFORE PERFORMING THIS PROCEDURE FAILURE TO FOLLOW THE WARNINGS AND CAUTIONS COULD RESULT IN POSSIBLE PERSONAL INJURY OR DEATH.

Before performing the following tests, refer to Cooling System 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 Heating and A/C System Self Diagnostics. If any diagnostic trouble codes (DTCs) are found in the body control module (BCM) or the powertrain control module (PCM), repair as necessary.

HEATER PERFORMANCE TEST

Heater Temperature Reference:

Engine coolant is delivered to the heater core through two heater hoses. With the engine idling at normal operating temperature, set the temperature control to the full hot position, the mode control to the floor position, and the blower motor control to the highest speed position. Using a test thermometer, check the temperature of the air being discharged at the HVAC housing floor outlets. Compare the test thermometer reading to the Heater Temperature Reference chart.

If the heater outlet air temperature is below the minimum specification, refer to Cooling System. Both of the heater hoses should be hot to the touch. The coolant return heater hose should be slightly cooler than the coolant supply heater hose. If the return hose is much cooler than the supply hose, locate and repair the engine coolant flow obstruction in the cooling system. Refer to Cooling System for more information.

OBSTRUCTED COOLANT FLOW
- Faulty water pump.
- Faulty thermostat.
- Pinched or kinked heater hoses.
- Improper heater hose routing.
- Plugged heater hoses or supply and return ports at the cooling system connections.
- A plugged heater core.
- Air locked heater core or air in cooling system.
If proper coolant flow through the cooling system is verified, and heater outlet air temperature is still low, a mechanical problem may exist.

MECHANICAL PROBLEMS
Possible locations or causes of insufficient heat:
- An obstructed cowl air intake.
- Obstructed heater system outlets.
- A faulty, obstructed or improperly installed blend-air door or actuator.
- A faulty blower system.
- A faulty A/C-heater control.

TEMPERATURE CONTROL
If the heater outlet air temperature cannot be adjusted with the temperature control on the heater-A/C control panel, the following could require service:
- A faulty A/C-heater control.
- Faulty blend door actuator.
- A faulty, obstructed or improperly installed blend-air door.
- An obstructed cowl air intake.
- The engine cooling system.