For 1990-2009 cars

### Test Description

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

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: HVAC Schematics. Connector End View Reference: Component Connector End Views. DEFINITION: The temperature cannot be adjusted, or cooling is insufficient during A/C operation.
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle.
2 | Check operation of air mix doors to make sure they are not jammed or broken Is the air mix door broken or jammed? | - | Go to HVAC Module Assembly Replacement. | Go to Step 3
3 | Important: All DTCs that are set must be diagnosed first unless you were sent to this diagnostic from a specific DTC diagnostic.

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 speed position?

--

Go to Step 4

Go to Blower Motor Inoperative.

4 | Does the blower motor operate at the desired speeds? | -- | Go to Step 5 | Go to Blower Motor Malfunction
5 |

1. Start the engine.
2. Place the mode switch in the face position.
3. Place the recirculation switch in the ON position.
4. Observe the recirculation door.
5. Place the recirculation switch in the OFF position.

Does the recirculation door move from the recirculation position to the outside air position?

--

Go to Step 6

Go to Symptoms - HVAC Systems - Automatic.

6 | Important: The ambient air temperature must be above 3°C (38°F).

1. Start the engine.
2. With a scan tool clear any DTCs that are stored in the HVAC control module.
3. Place the left air temperature switch in the coldest position.
4. Place the mode switch in the bi-level position.
5. Place the blower motor on high speed.

Does the A/C compressor operate?

--

Go to Step 7

Go to Air Conditioning Compressor Replacement.

7 | Perform the A/C system performance test. Refer to Air Conditioning (A/C) System Performance Test. Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 8
8 | Inspect the inside air temperature sensor for proper installation. Refer to Inside Air Temperature Sensor Replacement. Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 9
9 |

1. Turn ON the ignition, with the engine OFF.
2. Place the mode switch in face position.
3. Place the blower motor switch in maximum speed position.
4. Inspect for airflow through the inside air temperature sensor by placing a 5 cm (2 in) square piece of paper over the sensor air inlet.

Does the paper stay in place?

--

Go to Step 10

Go to Step 17

10 |

1. Install a thermometer near the inside air temperature sensor.
2. With a scan tool, observe the Inside Air Temp parameter in the Climate Control Panel data list.

Does the scan tool indicate the sensor temperatures is within 3°C (5°F) of the thermometer temperature?

--

Go to Step 11

Go to Step 14

11 |

1. Turn OFF the ignition.
2. Cover the sunload sensor.
3. Start the engine.
4. Adjust driver side temperature to 22°C (72°F).
5. With a scan tool, observe the Driver and Passenger Solar Sensor parameter in the Climate Control Panel Open/Short data list.

Is the Solar Sensor parameter greater than the specified value?

220 Counts

Go to Step 12

Go to Step 18

12 |

1. Uncover the sunload sensor.
2. Direct a light source at the sunload sensor.
3. Observe the Driver and Passenger Sunload parameter.

Do the counts change?

--

Go to Step 13

Go to Step 18

13 | Test the resistance of the ambient air temperature sensor. Refer to Sensor Resistance Table. Is the resistance near the value in the Sensor Resistance Table? | -- | Go to Testing for Intermittent Conditions and Poor Connections. | Go to Step 15
14 | Test the resistance of the inside air temperature sensor. Refer to Sensor Resistance Table. Is the resistance near the value in the Sensor Resistance Table? | -- | Go to Step 19 | Go to Step 17
15 | Inspect for poor connections at the harness connector of the ambient air temperature sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs. Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 17
16 | Inspect the aspirator tube for an air leak or obstruction. Did you find and correct the condition? | -- | Go to Step 24 | --
17 | Inspect for poor connections at the harness connector of the inside air temperature sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs. Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 20
18 | Inspect for poor connections at the harness connector of the sunload sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs. Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 21
19 | 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. Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 23
20 | Replace the inside air temperature sensor. Refer to Inside Air Temperature Sensor Replacement. Did you complete the replacement? | -- | Go to Step 24 | --
21 | Replace the sunload sensor. Refer to Sun Load Temperature Sensor Replacement. Did you complete the replacement? | -- | Go to Step 24 | --
22 | Replace the ambient air temperature sensor. Refer to Ambient Air Temperature Sensor Replacement. Did you complete the replacement? | -- | Go to Step 24 | --
23 | Replace the HVAC control module. Refer to Control Module References. Did you complete the replacement? | -- | Go to Step 24 | --
24 | Operate the system in order to verify the repair. Did you correct the condition? | -- | System OK | Go to Step 2