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

Is the action complete?

--

Go to Step 2

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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. Check 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

Check 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 15

1. Set the mode control to DEFROST.
2. Check 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 16

Turn the blower speed from the following positions:

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 17

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

Is the action complete?

--

Go to Step 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 25

Go to Step 24

Turn the blower speed from the following positions:

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 17

1. Turn the blower speed to HI.
2. Check 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. Check 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 18

Go to Step 10

Cycle the temperature door actuators with scan tool.

Did the temperature door actuators properly function?

--

Go to Step 11

Go to Step 19

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 14

Go to Step 12

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

Is the heater hoses location reversed?

--

Go to Step 20

Go to Step 13

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 26

Go to Step 23

Check the thermostat for proper installation.

Is the thermostat properly installed?

--

Go to Step 22

Go to Step 21

Check the mode door control and the stepper motors.

Is the action complete?

--

Go to Step 26

--

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

Is the action complete?

--

Go to Step 26

--

Refer to HVAC Blower Controls System Check .

Is the action complete?

--

Go to Step 26

--

1. Check 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 26

--

Repair or replace the temperature door stepper motors.

Is the action complete?

--

Go to Step 26

--

Reinstall the heater hoses in correct location.

Is the action complete

--

Go to Step 26

--

Reinstall the thermostat.

Is the action complete?

--

Go to Step 26

--

Replace the thermostat.

Is the action complete?

--

Go to Step 26

--

Replace heater core.

Is the action complete?

--

Go to Step 26

--

Check the temperature door stepper motors. Refer to Temperature Actuator Inoperative .

Is the action complete?

--

Go to Step 26

--

Check for system obstructions between blower and system outlets.

Is the action complete?

--

Go to Step 26

--

Perform the functional check. Refer to Functional Check .

Is the action complete?

--

System OK

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