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Heating Performance Diagnostic

Step

Action

Yes

No

DEFINITION: Heating system performance.

1

Were you sent here from Symptoms or another diagnostic table?

Go to Step 2

Go to Symptoms - HVAC Systems - Automatic

2

    Warning: Refer to Moving Parts and Hot Surfaces Warning in the Preface section.

  1. Turn ignition to on.
  2. Select vent mode.
  3. Select the warmest temperature setting.
  4. Select Maximum blower speed.
  5. Feel the temperature of the heater core inlet hose.

Does the heater core inlet hose feel warm to hot?

Go to Step 3

Go to Step 9

3
  1. Select the minimum blower speed.
  2. Feel the temperature of the heater core inlet and outlet hoses.

Does the heater core inlet hose feel warmer than the heater core outlet hose?

Go to Step 7

Go to Step 4

4
  1. Install a thermometer into the centre I/P panel air outlet.
  2. Secure a thermometer to the heater core outlet hose.
  3. Select the maximum blower speed.
  4. Record the temperature at the following location.
  5. Record the temperature at the following locations:
    6. • The centre I/P panel air outlet
    • The heater core outlet hose
  6. Compare the recorded temperatures.

Are the two temperature readings about equal?

Go to Step 5

Go to Step 6

5
  1. Inspect and repair the following areas of the vehicle for cold air leaks:
    2. • The scuttle
    • The recirculation door
    • The HVAC module case
  2. Perform the necessary repairs.

Are the repairs complete?

Go to Step 11

-

6
  1. Inspect the temperature door operation. Refer to Heating and Air Conditioning System Description and Operation .
  2. Perform any necessary repairs.

Are the repairs complete?

Go to Step 11

-

7
  1. Turn the ignition to off.
  2. Back-flush the heater core.
  3. Turn the ignition to on.
  4. Select the vent mode.
  5. Select the minimum blower speed.
  6. Select the warmest temperature setting.
  7. Feel the temperature of the heater core inlet and outlet hoses.

Does the heater core inlet hose feel warmer than the heater core outlet hose?

Go to Step 8

Go to Step 11

8

Replace the heater core. Refer to Heater Core Replacement .

Is the repair complete?

Go to Step 11

-

9

Inspect and repair the following areas:

    • Kinked hose
    • Heater valve inlet filter
    • Air in the coolant circuit
    • Inoperable heater valve

Did you find and correct the condition?

Go to Step 11

Go to Step 10

10

Inspect the coolant heater control module. Refer to Heating Performance Diagnostic .

Is the repair complete?

Go to Step 11

-

11

Operate the system in order to verify the repair.

Did you find and correct the condition?

System OK

Go to Step 2

   


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