For 1990-2009 cars

Step | Action | Yes | No
--- | --- | --- | ---
1 |

1. Engine idling.
2. Check for vacuum on the main vacuum supply source at the Heater and A/C Vacuum Valve

Is vacuum present?

Go to Step 2

Go to Step 11

2 |

1. Remove vacuum connector from Heater and A/C Vacuum Valve.
2. Using a vacuum pump, apply vacuum to each actuator line.

Do all the lines hold vacuum?

Go to Step 3

Go to Step 10

3 | Inspect the actuator doors for binding. Did you find and correct the condition? | Go to Step 20 | Go to Step 4
4 |

1. Ignition ON.
2. Disconnect the Heater and A/C Vacuum Valve solenoid connector.
3. With a test lamp connected to ground, probe TERMINAL "5".

Does the test lamp illuminate?

Go to Step 5

Go to Step 9

5 |

1. Ignition ON.
2. With a test lamp connected to voltage, probe TERMINAL "3" (CKT 1396).
3. The test lamp should only illuminate when the VENT, FRONT, MAX or NORM buttons are pushed. The test lamp should not illuminate with any other button pressed.

Did the test lamp illuminate only when the VENT, FRONT, MAX or NORM buttons were pushed?

Go to Step 6

Go to Step 12

6 |

1. Ignition ON.
2. With a test lamp connected to voltage, probe TERMINAL "4" (CKT 1397).
3. The test lamp should only illuminate when the OFF or HTR buttons are pushed. The test lamp should not illuminate with any other button pressed.

Did the test lamp illuminate only when the OFF or HTR buttons were pushed?

Go to Step 7

Go to Step 13

7 |

1. Ignition ON.
2. With a test lamp connected to voltage, probe TERMINAL "1" (CKT 1394).
3. The test lamp should only illuminate when the VENT, HTR, MAX, NORM or BI-LEVEL buttons are pushed. The test lamp should not illuminate with any other button pressed.

Did the test lamp illuminate only when the OFF or HTR buttons were pushed?

Go to Step 8

Go to Step 14

8 |

1. Ignition ON.
2. With a test lamp connected to voltage, probe TERMINAL "2" (CKT 1395).
3. The test lamp should only illuminate when the MAX button is pushed. The test lamp should not illuminate with any other button pressed.

Did the test lamp illuminate only when the MAX button was pushed?

Go to Step 17

Go to Step 15

9 | Repair the open or short to ground on circuit 41 | Go to Step 20 | --
10 | Inspect each vacuum line for an open or restriction, if no open or restriction was found replace the appropriate actuator. | Go to Step 20 | --
11 | Locate condition and restore vacuum to source line. | Go to Step 20 | --
12 | Inspect CKT 1396 for an open, short to ground, short to voltage or high resistance. Did you find and correct the condition? | Go to Step 20 | Go to Step 16
13 | Inspect CKT 1397 for an open, short to ground, short to voltage or high resistance. Did you find and correct the condition? | Go to Step 20 | Go to Step 16
14 | Inspect CKT 1394 for an open, short to ground, short to voltage or high resistance. Did you find and correct the condition? | Go to Step 20 | Go to Step 16
15 | Inspect CKT 1395 for an open, short to ground, short to voltage or high resistance. Did you find and correct the condition? | Go to Step 20 | Go to Step 16
16 | Inspect for poor connections at the harness connector of the Heater and A/C Control Assembly. | Go to Step 20 | Go to Step 18
17 | Inspect for poor connections at the harness connector of the Heater and A/C Vacuum Valve. | Go to Step 20 | Go to Step 19
18 | Replace the Heater and A/C Control Assembly. | Go to Step 20 | --
19 | Replace the Heater and A/C Vacuum Valve. | Go to Step 20 | --
20 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | --