For 1990-2009 cars

### Test Description

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

1. If the voltage ranges from 0.5 volts to 4.5 volts then the air temperature actuator is able to rotate and the HVAC control module has the ability to command the air temperature actuator.

2. The voltage will vary between 0-12 volts during normal operation. The HVAC control module connector must be connected during this step. The voltage should be monitored while air temperature actuator is commanded to move.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: HVAC Schematics DEFINITION: The temperature cannot be adjusted, or the cooling is insufficient during A/C operation.
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 each speed position.

Does the blower motor operate in any of the speed positions?

--

Go to Step 3

Go to Blower Motor Inoperative

3 | Does the blower motor operate in each speed position? | -- | Go to Step 4 | Go to Blower Motor Malfunction
4 | Turn the blower motor fan ON and select an air outlet mode. Is the air flow sufficient from the correct outlets in each mode? | -- | Go to Step 5 | Go to Air Delivery Improper
5 |

1. Place blower motor switch in any position except OFF.
2. Place mode switch to the floor position.
3. Place the air temperature switch from the coldest position to the warmest position.
4. Measure the voltage from the signal circuit of the air temperature actuator to a good ground.

Does the voltage measure within the specified values with a smooth transition from the coldest position to the warmest position?

0.5-4.5 V

Go to Step 6

Go to Step 7

6 | Inspect the air temperature door and the air temperature actuator for the following conditions:

• | A misaligned air temperature actuator.

| Refer to Air Temperature Actuator Replacement

• | Broken or binding linkages or air temperature door

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

• | Missing seals to the air temperature door

• | Misaligned seals to the air temperature door

Did you find and correct the condition?

--

Go to Step 19

System OK

7 |

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

Does voltage measure near the specified value?

5 V

Go to Step 8

Go to Step 12

8 | Inspect the air temperature door and the air temperature actuator for the following conditions:

• | A misaligned air temperature actuator.

| Refer to Air Temperature Actuator Replacement

• | Broken or binding linkages or air temperature door

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

• | Missing seals to the air temperature door

• | Misaligned seals to the air temperature door

Did you find and correct the condition?

--

Go to Step 19

Go to Step 9

9 |

1. Place blower motor switch in any position except OFF.
2. Place mode switch to the floor position.
3. Place the air temperature switch from the coldest position to the warmest position.
4. Measure the voltage from air temperature door control A circuit of the air temperature actuator and the air temperature door control B circuit of the air temperature actuator.

Does the voltage measure near specified value?

1-12 V

Go to Step 15

Go to Step 10

10 | Test the air temperature door control A circuit of the air temperature 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 air temperature door control B circuit of the air temperature 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 12
12 | Test the 5-volt reference circuit of the air temperature 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 air temperature actuator for an open or a high resistance. Refer to Circuit Testing and Wiring Repairs a 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 air temperature actuator for an open or a high resistance. Refer to Circuit Testing and Wiring Repairs a 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 air temperature 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 air temperature actuator. Refer to Air Temperature 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