For 1990-2009 cars

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. This step tests for a blower motor that does not operate regardless of the desired blower motor speed.

2. This step tests for a blower motor that operates, yet does not accurately respond to the desired blower motor speed.

3. This step verifies that there is power to the HVAC control assembly.

4. The voltage will vary between 0-5 volts during normal operation. The HVAC control assembly connector must be connected during this step.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views DEFINITION: Air does not flow correctly from the air distribution outlets.
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 |

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

Is the blower motor OFF?

--

Go to Step 3

Go to Blower Motor Always On

3 | Place the blower motor control in each speed position. Does the blower motor operate at all? | -- | Go to Step 4 | Go to Blower Motor Inoperative
4 | Does the blower motor operate correctly for each speed position? | -- | Go to Step 5 | Go to Blower Motor Malfunction
5 | Is the HVAC control assembly inoperative in all positions? | -- | Go to Step 6 | Go to Step 16
6 |

1. Observe the drive shaft of mode actuator .
2. Place the mode control in each mode position.

Does the mode actuator drive shaft rotate for each selected position?

--

Go to Step 7

Go to Step 8

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

• | Misaligned mode actuator

• | Broken linkages or binding linkages

• | A broken mode door or a binding mode door

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

Did you find and correct the condition?

--

Go to Step 23

Go to Testing for Intermittent Conditions and Poor Connections

8 | Test the ignition 1 voltage circuit of the mode actuator for an open or for a high resistance. Refer to Circuit Testing and to Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 9
9 | Test the ground circuit of the mode actuator for an open or high resistance. Refer to Circuit Testing and to Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 10
10 | Test the 5-volt reference circuit of the mode actuator for the following:

• | A short to ground

• | A short to voltage

• | A high resistance

• | An open

Refer to Circuit Testing and to Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 23

Go to Step 11

11 | Test the signal circuit of the mode door actuator for the following:

• | A short to ground

• | A short to voltage

• | A high resistance

• | An open

Refer to Circuit Testing and to Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 23

Go to Step 12

12 | Test the mode door control circuit of the mode actuator for the following:

• | A short to ground

• | A short to voltage

• | A high resistance

• | An open

Refer to Circuit Testing and to Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 23

Go to Step 13

13 | Important: Connect the mode actuator connector and the HVAC controller connector in order to correctly perform the test.

1. Turn ON the ignition, with the engine OFF.
2. Backprobe and monitor the voltage from the signal circuit of the mode door actuator with a test lamp that is connected to ground.
3. Connect a 3-ampere fused jumper between the mode door control circuit and the 5-volt reference circuit of the mode actuator. This action drives the motor to FLR mode.
4. Remove and reconnect the jumper between the mode door control circuit and the ground circuit of the mode actuator. This action drives the motor to DEF mode.

Does the mode actuator drive shaft rotate and does the voltage change?

--

Go to Step 14

Go to Step 18

14 |

1. Backprobe the mode actuator connector terminal in order to measure the voltage from the mode door control circuit to ground.
2. Place the mode control in each mode position.

Is the voltage measurement near the specified values for each setting?

0 V toward DEF

5 V toward FLR

2.5 V stationary

Go to Step 15

Go to Step 20

15 | Inspect the mode door for a mechanical condition or for a condition that allows excessive travel to the door. Did you find and correct the condition? | -- | Go to Step 23 | --
16 | Test the ignition 1 voltage circuit of the HVAC controller for an open, for a high resistance or for a short to ground. Refer to Circuit Testing and to Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 17
17 | Test the ground circuit of the HVAC controller for an open. Refer to Circuit Testing and to Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 20
18 | Inspect for bad connections at the harness connector of the mode actuator. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs . Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 19
19 |

1. Inspect the mode door and any attaching linkage for any binding.
2. Inspect the ductwork for any debris that would prevent airflow through the ductwork.

Did you find and correct the condition?

--

Go to Step 23

Go to Step 21

20 | Inspect for bad connections at the harness connector of the HVAC control assembly. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs . Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 22
21 | Replace the mode actuator. Refer to Mode Actuator Replacement . Did you complete the replacement? | -- | Go to Step 23 | --
22 | Replace the HVAC control assembly. Refer to Heater and Air Conditioning Control Replacement . Did you complete the replacement? | -- | Go to Step 23 | --
23 | Operate the system in order to verify the repair. Did you correct the condition? | -- | System OK | Go to Step 2