For 1990-2009 cars

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views DEFINITION: The temperature cannot be adjusted, or heating is insufficient.
1 | Did you perform the HVAC Diagnostic System Check? | -- | Go to Step 2 | Go to Diagnostic System Check - HVAC Systems - Automatic
2 | Place the blower motor switch in each speed position. Does the blower motor operate in any speed position? | -- | Go to Step 3 | Go to Blower Motor Inoperative
3 | Does the blower motor operate at the desired speeds? | -- | Go to Step 4 | Go to Blower Motor Malfunction
4 |

1. Start the engine.
2. Place the mode switch in the panel 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 5

Go to Air Recirculation Malfunction

5 | Does the Too Cold in vehicle condition occur when heating or defrosting is desired? | -- | Go to Step 6 | Go to Step 8
6 |

1. Start the engine.
2. Turn OFF the HVAC controls.

Does the A/C compressor operate?

--

Go to HVAC Compressor Clutch Does Not Disengage

Go to Step 7

7 | Inspect the cooling system for the following conditions:

• | A low coolant level

• | A loose or worn accessory drive belt

• | A leaking radiator hose or heater hose

• | A kinked radiator hose or heater hose

• | A missing radiator cap pressure seal

• | A leaking radiator cap

Refer to Heating Performance Diagnostic in Heating, Ventilation and Air Conditioning.

Did you find and correct the condition?

--

Go to Step 23

Go to Step 8

8 |

1. Place the mode switch in panel position.
2. Turn the ignition ON, with the engine OFF.
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 9

Go to Step 15

9 |

1. Install a thermometer near the inside air temperature sensor.
2. With a scan tool, observe the Inside Air Temp parameter in the General Info-Outputs data list.

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

--

Go to Step 10

Go to Step 13

10 |

1. Turn the ignition OFF.
2. Cover the ambient light sensor.
3. Turn the ignition ON.
4. With a scan tool, observe the Solar Sensor parameter in the Defrost data list.

Is the Solar Sensor parameter greater than the specified value?

220 counts

Go to Step 11

Go to Step 17

11 |

1. Uncover the ambient light sensor.
2. Direct a light source at the ambient light sensor.
3. Observe the Solar Sensor parameter in the Defrost data list.

Do the counts change?

--

Go to Step 12

Go to Step 17

12 | Test the resistance of the ambient air temperature sensor. Refer to Temperature Versus Resistance in Engine Controls - 3.0L or Temperature Versus Resistance in Engine Controls - 2.2L. Is the resistance near the value in the temperature vs resistance table? | -- | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 14
13 | Test the resistance of the inside air temperature sensor. Refer to Temperature Versus Resistance in Engine Controls - 3.0L or Temperature Versus Resistance in Engine Controls - 2.2L. Is the resistance near the value in the temperature vs resistance table? | -- | Go to Step 18 | Go to Step 16
14 | 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 in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 21
15 | Inspect the aspirator tube for a air leak or obstruction. Did you find and correct the condition? | -- | Go to Step 23 | --
16 | 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 in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 19
17 | Inspect for poor connections at the harness connector of the ambient light sensor. 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 23 | Go to Step 20
18 | 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 23 | Go to Step 22
19 | Replace the inside air temperature sensor. Refer to HVAC Control Module Replacement . Did you complete the replacement? | -- | Go to Step 23 | --
20 | Replace the ambient light sensor. Refer to Ambient Light Sensor Replacement in Lighting Systems. Did you complete the replacement? | -- | Go to Step 23 | --
21 | Replace the ambient air temperature sensor. Refer to Ambient Air Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 23 | --
22 | Replace the HVAC control module. Refer to HVAC Control Module 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