DIAGNOSIS AND TESTING - HEATER PERFORMANCE
Before performing the following tests, 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.
MAXIMUM HEATER OUTPUT
Engine coolant is delivered to the heater core through two heater hoses. With the engine idling at normal operating temperature, set the temperature control **** in the full hot position, the mode control switch **** in the floor position, and the blower motor switch **** in 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 Temperature Reference Chart.
Ambient Air Temperature 15.5° C (60° F) 21.1° C (70° F) 26.6° C (80° F) 32.2° C (90° F)
Minimum Air Temperature at Floor Outlet 52.2° C (126° F) 56.1° C (133° F) 59.4° C (139° F) 62.2° C (144° F)
If the floor outlet air temperature is too low, refer to Cooling to check the engine coolant temperature specifications. 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 for the procedures.
OBSTRUCTED COOLANT FLOW
Possible locations or causes of obstructed coolant flow:
•Faulty water pump.
•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.
If proper coolant flow through the cooling system is verified, and heater outlet air temperature is still low, a mechanical problem may exist.
Possible locations or causes of insufficient heat:
•A faulty blower system.
•A faulty heater-A/C control.
•An obstructed cowl air intake.
•Obstructed heater system outlets.
•A faulty, obstructed or improperly installed blend-air door or actuator.
If the heater outlet air temperature cannot be adjusted with the temperature control **** on the a/c heater control panel, the following could require service:
•The a/c heater control.
•A faulty blend door actuator.
•The blend door.
•Improper engine coolant temperature.
•Obstructed cowl air intake.
CONDITION POSSIBLE CAUSE CORRECTION
INSUFFICIENT HEATER OUTPUT.
1. Incorrect engine coolant level.
Check the engine coolant level.
2. Air trapped in engine cooling system.
3. Incorrect engine coolant temperature.
Check the performance and operation of the engine cooling system including: thermostat, water pump, fan drive, accessory drive belt, coolant flow (plugged radiator or heater core, plugged or kinked coolant hoses).
4. Blend air door actuator not operating properly.
5. Blend-air door not operating properly.
6. Insufficient air flow through heater housing.
7. Improper blower motor operation.