1. Inspect the following items:

•	The coolant level

•

The belts

•	The belt tension

•	The surge tank cap

2. Inspect the hoses for leaks or kinks.
3. Adjust the heater control to the HEATER mode.
4. Set the blower control to the HIGH position.
5. Set the temperature control to the FULL HOT position.
6. Turn the ignition switch to the ON position.
7. Inspect for airflow out of the heater outlet.
8. Inspect the outlet attachment.

Is the airflow high?

--

Go to Step 2

Go to Step 20

Inspect the blower speeds for a change in the airflow.

Does the speed of the airflow change?

--

Go to Step 3

Go to Heater Blower Controls System Check

1. Adjust the heater control to the HEATER mode.
2. Set the blower control to the HIGH position.
3. Set the temperature control to the FULL HOT position.

Caution: The cooling system is pressurized when hot.

4. After the engine is sufficiently cool, remove the cooling system pressure cap.
5. Start the engine. Idle the engine until the upper radiator hose is warm.
6. Install the pressure cap.
7. With the engine warm, drive the vehicle at 48 kph (30 mph). Ensure that the total warm up time equals 20 minutes.
8. Use a thermometer in order to measure the ambient air temperature.
9. Measure the discharge air temperature at the heater outlet.
10. Compare the 2 temperatures to the above table.

Is the heater temperature low according to the table?

--

Go to Step 5

Go to Step 4

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

•

The dash

•	The heater cases

•

The vents

2. Inspect under the seat for obstructions.
3. Repair any leaks or obstructions as needed.

Does the condition persist?

--

Go to Step 5

System OK

1. Turn the ignition switch to the ON position.
2. Move the temperature control from the FULL COLD position to the FULL HOT position.
3. Listen for the temperature valve operation.

Does the temperature valve appear to be operating?

--

Go to Step 6

Go to Step 17

Verify the temperature valve operation.

Is the temperature valve operating?

--

Go to Step 8

Go to Step 7

Inspect for the following conditions. Repair the components as needed:

Does the condition persist?

--

Go to Step 8

System OK

1. Set the temperature control to the FULL HOT position.
2. Start the vehicle.
3. Warm the vehicle to operating temperature.
4. Feel the inlet hose and the outlet hose.

Are both hoses warm?

--

Go to Step 9

Go to Step 12

Inspect the thermostat for the following conditions:

Is the installation OK?

--

Go to Step 10

Go to Step 11

Replace the thermostat. Refer to Engine Coolant Thermostat Replacement in Engine Cooling.

Is the repair complete?

--

System OK

--

1. Reinstall the thermostat.
2. Verify proper installation.

Is the repair complete?

--

System OK

--

The outlet hose is hot and the inlet hose is warm.

1. Remove the hoses at the heater core.
2. Inspect for proper installation of the hoses.

Are the hoses installed in reverse?

--

Go to Step 13

Go to Step 14

1. Properly install the hoses.
2. Retest the system.

Does the condition persist?

--

Go to Step 14

System OK

1. Drain the engine coolant.
2. Backflush the heater core.
3. Replace the engine coolant.
4. Retest the system.

Are both hoses warm?

--

Go to Step 15

Go to Step 16

Replace the heater core. Refer to Heater Core Replacement .

Is the repair complete?

--

System OK

--

Is the inlet hose hot and the outlet hose warm?

--

System OK

--

Inspect the connection on the temperature valve actuator.

Is the temperature valve actuator connected?

--

Go to Step 19

Go to Step 18

1. Connect the temperature valve actuator.
2. Verify proper operation of the system.

Is the system operating properly?

--

System OK

--

1. Inspect the following components:

•	The actuator electrical circuit

•	The cable linkage

2. Repair or replace the components as needed.

Is the system operating properly?

--

System OK

--

The airflow is low or nonexistent.

Perform the HVAC functional inspection. Refer to Function Test .

Does the condition persist?

--

Go to Step 21

System OK

Inspect the airflow out of the followin outlets:

Is the airflow out of the defroster outlets or the vent outlets high?

--

Go to Step 22

Go to Step 23

1. Inspect for the following conditions:

•	A restricted heater defroster valve

•	A restricted mode valve

2. Repair or replace the valves as needed.

Is the repair complete?

--

System OK

--

The airflow out of the defroster outlets or the vent outlets is low or nonexistent.

1. Switch the mode to DEFROSTER.
2. Inspect the airflow.

Is the defroster airflow OK?

--

Go to Step 24

Go to Step 25

1. Remove the heater outlet.
2. Inspect the heater for obstructions.
3. Remove any obstructions as needed.

Does the system operate properly?

--

System OK

--

Inspect the blower speeds for airflow changes.

Are the speed changes OK?

--

Go to Step 26

Go to Heater Blower Controls System Check

Inspect the system for obstructions at the blower inlet and the plenum.

Did you find any obstructions?

--

Go to Step 27

Go to Step 28

Remove the obstructions as needed.

Does the system operate properly?

--

System OK

--

1. Set the blower to the HIGH position.
2. Move the temperature control from the FULL HOT position to the FULL COLD position.
3. Listen for a change in the air flow.

Did a change in the airflow occur?

--

Go to Step 29

Go to Step 30

1. Inspect the system for an obstruction between the blower and the system outlets.
2. Remove any obstruction as needed.

Does the system operate properly?

--

System OK

--

1. Inspect the temperature valve and the actuator for proper operation.
2. Repair the components as needed.

Does the system operate properly?

--

System OK

--

-18°C (0°F)

54°C (130°F)

-4°C (25°F)

59°C (139°F)

10°C (50°F)

64°C (147°F)

24°C (75°F)

68°C (155°F)