For 1990-2009 cars

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: HVAC Schematics DEFINITION: Air does not flow correctly from the air distribution outlets.
1 | Did you review the HVAC operation and perform the necessary inspections? | -- | Go to Step 2 | Go to Symptoms - HVAC Systems - Manual
2 |

1. Turn ON the ignition, with the engine OFF.
2. Place the blower motor switch in the OFF position.

Is the blower motor OFF?

--

Go to Step 3

Go to Blower Motor Always On

3 | Place the blower motor switch in each speed position. Does the blower motor operate in any of the speed positions? | -- | Go to Step 4 | Go to Blower Motor Inoperative
4 | Does the blower motor operate in each speed position? | -- | Go to Step 5 | Go to Blower Motor Malfunction
5 | Place the mode switch in each mode position. Is the airflow sufficient from the correct outlets in each mode? | -- | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 6
6 |

1. Place blower motor switch in any position but OFF.
2. Adjust the mode switch from vent to defrost.
3. Measure the voltage from mode door control A circuit of the mode actuator and the mode door control B circuit of the mode actuator.

Does the voltage measure near specified value?

1-12 V

Go to Step 7

Go to Step 10

7 |

1. Disconnect mode actuator.
2. Measure the voltage from the 5-volt reference circuit of the mode actuator to a good ground.

Does voltage measure near the specified value?

5 V

Go to Step 8

Go to Step 12

8 | Important: Ensure the mode actuator connector is connected during this step in order to avoid misdiagnosis.

1. Connect the mode actuator connector.
2. Place blower motor switch in any position except OFF.
3. Adjust the mode switch from vent to defrost.
4. Measure the voltage from the signal circuit of the mode actuator to a good ground.

Does the voltage measure within the specified values with a smooth transition between vent and defrost?

0.5-4.5 V

Go to Step 9

Go to Step 13

9 | Inspect the mode door and the mode actuator for the following conditions:

• | A misaligned mode actuator

| Refer to Mode Actuator Replacement .

• | Broken or binding linkages or mode door

• | An obstruction that prevents the mode door from operating within its full range of motion

• | Missing seals to the mode door

• | Misaligned seals to the mode door

Did you find and correct the condition?

--

Go to Step 19

Go to Step 15

10 | Test the mode door control A circuit of the mode actuator for an open, high resistance, short to ground, or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 11
11 | Test the mode door control B circuit of the mode actuator for an open, high resistance, short to ground, or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 16
12 | Test the mode actuator 5-volt reference circuit of the mode actuator for an open, high resistance, short to ground, or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 13
13 | Test the signal circuit of the mode actuator for an open or a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 14
14 | Test the low reference circuit of the mode actuator for an open or a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 16
15 | Inspect for poor connections at the harness connector of the mode actuator. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 17
16 | Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 18
17 | Replace the mode actuator. Refer to Mode Actuator Replacement . Did you complete the replacement? | -- | Go to Step 19 | --
18 | Replace the HVAC control module. Refer to HVAC Control Module Replacement . Did you complete the replacement? | -- | Go to Step 19 | --
19 | Operate the system in order to verify the repair. Did you correct the condition? | -- | System OK | Go to Step 2