For 1990-2009 cars

Step | Action | Yes | No
--- | --- | --- | ---
Caution: Refer to Radiator Cap Removal Caution in the Preface section.
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 | Check the coolant level. Is the coolant level correct? | Go to Step 4 | Go to Step 3
3 | Add coolant, as needed. Is the repair complete? | System OK | Go to Step 4
4 | Check the timing belt for tension or damage. Is the timing belt OK? | Go to Step 6 | Go to Step 5
5 | Correct any problem with the drive belts. Is the repair complete? | System OK | Go to Step 6
6 | Check the coolant hoses for leaks or kinks. Are the coolant hoses OK? | Go to Step 8 | Go to Step 7
7 | Repair any problem with the coolant hoses. Is the repair complete? | System OK | Go to Step 8
8 | Check the surge tank cap. Is the surge tank cap OK? | Go to Step 10 | Go to Step 9
9 | Repair or replace the surge tank cap, as needed. Is the repair complete? | System OK | Go to Step 10
10 |

1. Set the A/C switch to OFF on vehicles equipped with air conditioning.
2. Set the blower motor switch on 4.
3. Set the heater control to full hot.
4. Turn the ignition ON.
5. Check for airflow from the heater outlet.

Is there heavy airflow from the heater outlet?

Go to Step 11

Go to Step 26

11 | Check for a change in the airflow at various blower speeds. Does the blower speed increase as the switch is turned from 1 to 4? | Go to Step 12 | Go to Blower Motor Malfunction
12 |

1. Set the A/C switch to OFF on vehicles equipped with air conditioning.
2. Set the temperature lever to full hot.
3. Set the blower motor switch on 4.
4. With the engine sufficiently cool, remove the surge tank cap.
5. Start the vehicle and idle the engine.
6. Watch for the flow of the coolant.

Is the coolant flow visible?

Go to Step 14

Go to Step 13

13 |

1. Check for the following problems:

• | Restriction in the cooling system

• | Failed water pump impeller

• | Faulty thermostat

2. Make repairs to the cooling system, as needed.

Are the repairs complete?

System OK

Go to Step 14

14 |

1. Install the surge tank cap.
2. With the ignition ON, allow the engine to warm up for about 20 minutes. Drive the vehicle at 48 km/h (30 mph).
3. Use a thermometer to measure the ambient air temperature and the discharge air temperature at the heater outlet. Refer to HVAC Preliminary Checks .

Does the heater output meet the minimum values given?

Go to Step 15

Go to Step 16

15 |

1. Check the vehicle for cold air leaks at the following locations:

• | Dash

• | Heater cases

• | Vents

2. Check under the seat for obstructions.
3. Repair any leaks or obstructions.

Is the repair complete?

System OK

--

16 |

1. Turn the ignition OFF.
2. Turn the temperature control knob to full cold, then rapidly to full hot.
3. Listen for the sound of the temperature door slam just before it reaches the end of the travel range of the control knob.

Does the door slam?

Go to Step 18

Go to Step 17

17 |

1. Check the temperature door for the following:

• | Travel

• | Cables

• | Linkage

2. Verify the accuracy of the temperature controls at full hot.
3. Verify the accuracy of the temperature controls at full cold.

Is the repair complete?

System OK

--

18 |

1. Set the temperature door to full hot.
2. Start the vehicle.
3. Check the temperature of the heater inlet hose and the heater outlet hose by feel. The air temperature around the hoses should be at least 29°C (84°F).

Is the heater inlet hose hot and the heater outlet hose warm?

Go to Step 19

Go to Step 22

19 | Check the thermostat. Is the thermostat installed and seated properly? | Go to Step 20 | Go to Step 21
20 | Replace the thermostat. Is the repair complete? | System OK | --
21 | Reinstall the thermostat. Is the repair complete? | System OK | --
22 | Inspect the heater hoses for proper installation. Are the heater hoses reversed? | Go to Step 23 | Go to Step 24
23 | Reinstall the heater hoses properly. Is the repair complete? | System OK | --
24 |

1. Back flush the heater core.
2. Drain the cooling system.
3. Replace the coolant.
4. Warm the engine to an average operating temperature.
5. Feel the heater inlet hose and the heater outlet hose.

Is the heater inlet hose hot and the heater outlet hose warm?

System OK

Go to Step 25

25 | Replace the heater core. Is the repair complete? | System OK | --
26 | Recheck the system using the Control Settings/Correct Results tests. Is the repair complete? | System OK | Go to Step 27
27 | Check for airflow from the defroster or the vent outlets. Is there high airflow from the defroster or vent outlets? | Go to Step 28 | Go to Step 29
28 | Adjust the heater door at the floor and the vent door to get the proper airflow. Is the repair complete? | System OK | --
29 | Switch the mode knob to defrost. Is the defroster airflow OK? | Go to Step 30 | Go to Step 31
30 |

1. Remove the heater outlet and check for obstructions.
2. Remove any obstructions in the heater outlet.

Is the repair complete?

System OK

--

31 | Check for airflow change at various blower speeds. Does the blower speed increase as the control is turned from 1 to 4? | Go to Step 32 | Go to Blower Motor Malfunction
32 | Check for obstructions in the system at the blower inlet. Are there any obstructions? | Go to Step 33 | Go to Step 34
33 | Remove the obstructions in the system at the blower inlet. Are the repairs complete? | System OK | --
34 |

1. Set the blower on 4.
2. Rotate the temperature control from full hot to full cold.
3. Listen for an airflow change.

Does the airflow change?

Go to Step 35

Go to Step 36

35 |

1. Check the temperature door for the following:

• | Travel

• | Cables

• | Linkage

• | Control

2. Verify the accuracy of the temperature control at full hot.

Is the repair complete?

System OK

--

36 |

1. Check the system for any obstruction between the blower and the system outlets.
2. Remove any obstruction.

Is the repair complete?

System OK

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