GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2007 🢒 Lucerne 🢒 HVAC 🢒 HVAC - Automatic 🢒 Too Cold in Vehicle

Test Description

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

  1. This test resets the HVAC control module and checks for current air temperature actuator DTC.

    2.

  2. This checks for proper operation of coolant system to ensure heater output.

Step

Action

Values

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

DEFINITION: The temperature cannot be adjusted, or the heating is insufficient.

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the current DTC list for the HVAC Module.

Does the scan tool display DTC B0408, B0409, B0419, or B0423?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

Go to Step 3

3

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 Malfunction

4

Does the blower motor operate at the desired speeds?

--

Go to Step 5

Go to Blower Motor Malfunction

5
  1. Place the blower motor switch in the maximum speed position.
  2. Place the mode controls in the BI-LEVEL position.
  3. Alternately, place the recirculation switch in the outside air and recirculation positions.

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

--

Go to Step 6

Go to Air Delivery Improper

6

Place the passenger temperature switch in the OFF position.

Does the Too Cold in Vehicle concern occur when heating or defrosting is desired?

--

Go to Step 7

Go to Step 9

7
  1. Start the engine.
  2. Place the HVAC control module in the OFF position.

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

Did you find and correct the condition?

--

Go to Step 26

Go to Step 9

9

Inspect the upper left, upper right, lower left, and lower right air temperature sensors for the following conditions:

    • An obstruction to the airflow
    • A damaged or a missing seal in the sensor
    • Misaligned air ducts
    • A misaligned sensor

Did you find and correct the condition?

--

Go to Step 26

Go to Step 10

10
  1. Turn ON the ignition, with the engine OFF.
  2. Inspect for airflow through the inside air temperature assembly 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 11

Go to Step 14

11
  1. Install a thermometer near the upper left, upper right, lower left, and lower right air sensors and the inside air temperature assembly.
  2. With a scan tool, observe the Inside Air Temp. data parameter in the Instrument Panel Module data list:

Does the scan tool indicate that the sensor temperatures are within the specification at the thermometer temperatures?

-3 to +3°C (-5 to +5°F)

Go to Step 12

Go to Step 17

12
  1. Turn the engine OFF.
  2. Install a scan tool.
  3. Cover the sunload sensor.
  4. Start the engine.
  5. Place the driver side temperature to 22°C (72°F).
  6. With a scan tool, observe the Solar Sensor data parameter in the HVAC Automatic data list.

Does the scan tool indicate that the solar sensor parameter is greater than the specified value?

224 Counts

Go to Step 13

Go to Step 19

13
  1. Uncover the sunload sensor.
  2. Direct a light source at the sunload sensor.

Do the counts change?

--

System OK

Go to Step 19

14
  1. Disconnect the inside air temperature assembly.
  2. Turn ON the ignition, with the engine OFF.
  3. Connect a test lamp between the ignition 3 circuit of the inside air temperature assembly and the inside air temperature assembly control circuit of the inside air temperature assembly.

Does the test lamp illuminate?

--

Go to Step 18

Go to Step 15

15

Test the ignition 3 voltage circuit of the inside air temperature assembly for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 26

Go to Step 16

16

Test the inside air temperature assembly control circuit of the inside air temperature assembly for the following conditions:

    • A short to voltage
    • A high resistance
    • An open
        Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 26

Go to Step 20

17

Test the suspect temperature sensor resistance.

Does the resistance measure near the Sensor Resistance Table?

--

Go to Step 21

Go to Step 18

18

Inspect for poor connections at the harness connector of the 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 26

Go to Step 22

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 26

Go to Step 23

20

Inspect for poor connections at the harness connector of the HVAC module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 26

Go to Step 24

21

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 26

Go to Step 25

22

Replace the temperature sensor. Refer to Inside Air Temperature Sensor Replacement .

Did you complete the replacement?

--

Go to Step 26

--

23

Replace the sunload sensor. Refer to Sun Load Sensor Replacement .

Did you complete the replacement?

--

Go to Step 26

--

24

Replace the DIM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 26

--

25

Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 26

--

26

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 3