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 Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 | Place the blower motor switch in each speed position. Does the blower motor work in any speed position? | -- | Go to Step 3 | Go to Blower Motor Malfunction
3 | Does blower motor run in the desired speed position? | -- | Go to Step 4 | Go to Blower Motor Malfunction
4 |

1. Install a scan tool.
2. Turn ON the ignition, with the engine OFF.
3. With a scan tool, command pump control device to connect in the special function, complex test of temperature control panel.

Does the rear boil coolant pump work?

--

Go to Step 5

Go to Rear Boil Coolant Pump Operation

5 |

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 6

Go to Air Recirculation Malfunction

6 | Place the passenger temperature switch in the OFF position. Does the too cold in vehicle condition occur when heating or defrosting is desired? | -- | Go to Step 7 | Go to Step 9
7 |

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 8

8 | 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 .

Did you find and correct the condition?

--

Go to Step 25

Go to Step 9

9 |

1. Place the mode switch in PANEL position.
2. Turn ON the ignition, with the engine OFF.
3. Place the blower motor switch in maximum speed position.
4. Inspect for air flow 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 16

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. Turn ON the ignition.
4. 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 19

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 19

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 20 | Go to Step 18
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 25 | Go to Step 17
16 | Inspect the aspirator tube for a air leak or obstruction. Did you find and correct the condition? | -- | Go to Step 25 | --
17 | 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 25 | Go to Step 23
18 | 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 25 | Go to Step 21
19 | 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 25 | Go to Step 22
20 | 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 25 | Go to Step 24
21 | Replace the inside air temperature sensor. Refer to Inside Air Temperature Sensor Replacement . Have you finished the replacement? | -- | Go to Step 25 | --
22 | Replace the sunload sensor. Refer to Sun Load Sensor Replacement . Have you finished the replacement? | -- | Go to Step 25 | --
23 | Replace the ambient air temperature sensor. Refer to Ambient Air Temperature Sensor Replacement . Have you finished the replacement? | -- | Go to Step 25 | --
24 | Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming. Have you finished the replacement? | -- | Go to Step 25 | --
25 | Operate the system in order to verify the repair. Did you correct the condition? | -- | System OK | Go to Step 2