For 1990-2009 cars

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Caution: Refer to Radiator Cap Removal Caution in the Preface section.
1 | Verify the customer’s complaint. Are the customer’s concerns verified? | -- | Go to Step 2 | System OK
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 drive belts for tension or damage. Are the drive belts 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 for leaks. Is the surge tank cap OK? | -- | Go to Step 10 | Go to Step 9
9 | Replace the surge tank cap as needed. Is the repair complete? | -- | System OK | Go to Step 10
10 |

1. Turn the A/C switch OFF.
2. Set the blower motor switch on maximum speed.
3. Set the heater control to full hot.
4. Turn the ignition ON.
5. Check for airflow from the vent 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 minimum to maximum? | -- | Go to Step 12 | Go to Blower Motor Inoperative
12 |

1. Turn the A/C switch OFF.
2. Set the temperature lever to full hot.
3. Set the blower motor switch on maximum speed.
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).

Does the heater output meet the minimum values given?

-18° C (0°F)

-4°C (25°F)

10°C (50°F)

24°C (75°F)

Heater Outlet

54°C (129°F)

59°C (138°F)

64°C (147°F)

68°C (154°F)

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.

Are the repairs 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 following aspects of the temperature door:

• | 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 control knob 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. Refer to Thermostat Diagnosis . Is the thermostat installed and seated properly? | -- | Go to Step 20 | Go to Step 21
20 | Replace the thermostat. Refer to Engine Coolant Thermostat Replacement . 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. Refer to Heater Core Replacement . Is the repair complete? | -- | System OK | --
26 | Recheck the system using the "Control Settings/Correct Results" tests. Refer to Air Delivery Improper for the automatic system, Air Delivery Improper for the manual system, Improper Control Response for the automatic system, Improper Control Response for the manual system.

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 |

1. Check the heater door at the floor and the vent door to get the proper airflow and to verify proper operation.
2. Repair as required.

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 1-4? | -- | Go to Step 32 | Go to Air Delivery Improper
32 | Check for obstructions in the system at the blower inlet and at the air filter, if the vehicle is equipped with one. Are there any obstructions? | -- | Go to Step 33 | --
33 | Remove the obstructions in the system at the blower inlet or replace a clogged filter. Is the repair complete? | -- | System OK | --
34 |

1. Set the blower on maximum speed.
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 following aspects of the temperature door:

• | Travel

• | Cables

• | Linkage

• | Control

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

Is the repair complete?

--

Go to Step 1

--

36 |

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

Is the repair complete?

--

Go to Step 1

--