For 1990-2009 cars

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 |

1. Inspect the engine coolant level.
2. Inspect the coolant pump drive belt tension.
3. Inspect the radiator and the heater hoses for leaks and kinks.
4. Inspect the radiator cap for proper operation.
5. Inspect for operation of electric auxiliary water pump with key on.

Is the action complete?

--

Go to Step 2

--

2 |

1. Set the mode to HEAT.
2. Set the blower speed to HI.
3. Set the temperature control to full HOT.
4. Turn the ignition switch to ON.
5. Inspect for airflow out of the heater outlet?

Is the airflow low or no airflow out of the heater outlet?

--

Go to Step 3

Go to Step 8

3 | Inspect for airflow out of defroster or vent outlets. Is the air flow low or no airflow out of the defroster or vent outlets? | -- | Go to Step 4 | Go to Step 16
4 |

1. Set the mode control to DEFROST.
2. Inspect for airflow out of the defroster outlets.

Is the air flow low or no airflow out of the defroster outlets?

--

Go to Step 5

Go to Step 17

5 | Turn the blower speed from the following positions:

• | OFF to LO

• | MED-LO

• | MED-HI

• | HI

• | Then back to OFF.

Does the blower motor speed increases at each speed level when blower speed is turned to HI and then decreases as the switch is moved towards LO?

--

Go to Step 6

Go to Step 18

6 |

1. Inspect for system obstructions at blower inlet and plenum.
2. Repair as necessary.

Is the action complete?

--

Go to Step 7

--

7 |

1. Turn the blower speed to HI.
2. Turn the temperature control from full HOT to full COLD.

Did you hear any airflow changes?

--

Go to Step 26

Go to Step 25

8 | Turn the blower speed from the following positions:

• | OFF to LO

• | MED-LO

• | MED-HI

• | HI

• | Then back to OFF

Does the blower motor speed increases at each speed level when blower speed is turned to HI and then decreases as the switch is moved towards LO?

--

Go to Step 9

Go to Step 18

9 |

1. Turn the blower speed to HI.
2. Inspect the ambient air temperature with the thermometer.
3. Drive the vehicle at 48 km/h (30 mph). The minimum engine warm-up time: 20 minutes.
4. Inspect the following discharge air temperature at heater outlet temp @ ambient temp:

• | 54°C (130°F) @ -18°C (0°F)

• | 59°C (139°F) @ -4°C (25°F)

• | 64°C (147°F) @ 10°C (50°F)

Is the heater outlet temperature within specified value?

--

Go to Step 19

Go to Step 10

10 | Cycle the temperature door actuators with scan tool. Did the temperature door actuators properly function? | -- | Go to Step 11 | Go to Step 19
11 | Refer to DTC 10 Inside Air Temperature Sensor Voltage Low for temperature sensor diagnosis. Is the action complete? | -- | Go to Step 12 | --
12 |

1. Set the temperature control to full HOT.
2. Start the engine.
3. Feel the inlet and the outlet heater hoses.

Does the inlet heater hose feel hot and the outlet heater hose feel warm?

--

Go to Step 15

Go to Step 13

13 |

1. Disconnect the heater hoses at heater core.
2. Inspect for proper heater hose location.

Is the heater hoses location reversed?

--

Go to Step 21

Go to Step 14

14 |

1. Flush the heater core.
2. Drain and refill the cooling system.
3. Set the temperature control to full HOT.
4. Start the engine.
5. Feel the inlet and the outlet heater hoses.

Does the inlet heater hose fool hot and the outlet heater hose feel warm?

--

Go to Step 27

Go to Step 24

15 | Inspect the thermostat for proper installation. Is the thermostat properly installed? | -- | Go to Step 23 | Go to Step 22
16 | Inspect the mode door control and the stepper motors. Is the action complete? | -- | Go to Step 27 | --
17 |

1. Inspect for obstructions in heater outlet.
2. Repair as necessary.

Is the action complete?

--

Go to Step 27

--

18 | Refer to DTC 27 Blower Motor Voltage Low or Open Circuit for blower motor diagnosis. Is the action complete? | -- | Go to Step 27 | --
19 |

1. Inspect the vehicle for cold air leaks at the following areas:

• | The I/P

• | The heater case

• | The front vents

2. Repair as necessary.

Is the action complete?

--

Go to Step 27

--

20 | Repair or replace the temperature door stepper motors. Is the action complete? | -- | Go to Step 27 | --
21 | Reinstall the heater hoses in correct location. Is the action complete | -- | Go to Step 27 | --
22 | Reinstall the thermostat. Refer to Thermostat Replacement in Engine Cooling. Is the action complete? | -- | Go to Step 27 | --
23 | Replace the thermostat. Is the action complete? | -- | Go to Step 27 | --
24 | Replace heater core. Refer to Air Conditioning Evaporator Core Replacement Is the action complete? | -- | Go to Step 27 | --
25 | Inspect the temperature door stepper motors. Refer to DTC 16 Int Air Mix Door Mtr Volts Low/Open Circuit . Is the action complete? | -- | Go to Step 27 | --
26 | Inspect for system obstructions between blower and system outlets. Is the action complete? | -- | Go to Step 27 | --
27 | Perform the functional test. Is the action complete? | -- | System OK | --