For 1990-2009 cars

This procedure provides a test of all functions of the heater/defroster unit.

1. Warm up the vehicle.
2. Keep the engine running.
3. Perform the test outlined in the table below and look for the results indicated.

Control Settings | Correct Results
--- | ---
Mode Knob | Temp Control | Blower Motor Switch | Blower Speed | Side Vent Outlet | Center Vent Outlet | Floor Outlet | Defrost Outlet | Side Window Outlet
Vent | Cold | Off | Off | No Airflow | No Airflow | No Airflow | No Airflow | No Airflow
Vent | Cold | 4 High | Ambient Airflow | Ambient Airflow | No Airflow | No Airflow | No Airflow | No Airflow
Vent | Cold to Hot | 4 | High | Minimum Cold to Hot Airflow | No Airflow | Cold to Hot Airflow | Minimum Cold to Hot Airflow | Minimum Cold to Hot Airflow
Defroster | Cold to Hot | 4 | High | Minimum cold to Hot Airflow | No Airflow | Minimum Cold to Hot Airflow | Cold to Hot Airflow | Minimum Cold to Hot Airflow

If any of these settings does not produce the correct results, perform the following diagnostic procedure.

Step | Action | Yes | No
--- | --- | --- | ---
1 | Verify the customers complaint. Are the customers concerns verified? | Go to Step 2 | System OK
2 |

1. Examine the affected door in the unit for proper attachment to the vacuum actuator.
2. Check the actuator connection to the door.
3. Check that the vacuum hose is properly connected.

Is everything connected properly?

Go to Step 4

Go to Step 3

3 | Repair as necessary. Is the repair complete? | System OK | --
4 |

1. Disconnect the actuator at the door.
2. Check the range of the door travel and the effort required to move it.

Does the door move freely through its entire range of travel so that it can close at both ends of the range?

Go to Step 5

Go to Step 3

5 | Check the travel of the actuator by turning the control knob with the engine running. Is the actuator OK? | Go to Step 6 | Go to Step 7
6 |

1. Reinstall the actuator.
2. Recheck the system using the "Control Settings/Correct Results" tests in this procedure.

Does the system perform properly?

System OK

Go to Step 9

7 |

1. Check the vacuum hose at the control.
2. Check for a broken control.

Is there a problem with the vacuum hose or the control?

Go to Step 8

Go to Step 9

8 | Repair the vacuum hose or the control as necessary. Is the repair complete? | System OK | Go to Step 9
9 | Recheck the system using the "Control Settings/Correct Results" test in this procedure. Is the repair complete? | System OK | Go to Step 10
10 | Check for airflow from the defroster or the vent outlets. Is the high airflow from the defroster or the vent outlets? | Go to Step 11 | Go to Step 12
11 | Adjust the heater door at the floor and the vent door to get the proper airflow. Is the repair complete? | System OK | --
12 | Switch the mode knob to defrost. Is the defroster airflow OK? | Go to Step 13 | Go to Step 14
13 |

1. Remove the heater outlets.
2. Check the heater outlets for obstructions.
3. Remove any obstructions in the heater outlets.

Is the repair complete?

System OK

--

14 | Check the blower speeds for change in airflow. Does the blower speed increase as the control is turned from 1 to 4? | Go to Step 15 | Refer to Blower Motor Inoperative
15 |

1. Check for obstructions in the system at the blower inlet and check the air filter if the vehicle is equipped.
2. Remove any obstructions at the blower inlet and replace the filter if it is clogged.

Is the repair complete?

System OK

Go to Step 16

16 |

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 17

Go to Step 18

17 |

1. Check the temperature door, the cable, the linkage, and the control.
2. Adjust the temperature control to full hot.

Is the repair complete?

System OK

--

18 |

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

Is the repair complete?

System OK

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