GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2001 🢒 Chevy Suburban - 2WD 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 Too Cold in Vehicle - Auxiliary

Too Cold in Vehicle - Auxiliary w/o sunroof

Test Description

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

  1. This step ensures that the primary HVAC system is functioning properly.

    2.

  2. The DTC's listed could set if a calibration of the actuators is performed.

    3.

  3. If the condition does not occur when a heating request has been made then you must bypass the A/C compressor and cooling system diagnostic information.

    4.

  4. This step ensures that the rear auxiliary HVAC control module is able to move the auxiliary air temperature actuator.

    5.

  5. This step ensures that the front auxiliary HVAC control assembly is able to move the auxiliary air temperature actuator.

    6.

  6. The infrared sensor is located between the auxiliary blower motor switch and the auxiliary temperature switch on rear auxiliary HVAC control module. It has a glass cover protecting the sensor which is integral to the rear auxiliary HVAC control module.

Step

Action

Values

Yes

No

Schematic Reference: HVAC Schematics

DEFINITION: Auxiliary air temperature can not be adjusted from one or both auxiliary controls or auxiliary 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

Important:: The auxiliary HVAC control assembly operates independently of the HVAC control module to provide heated airflow through the auxiliary system.

Does the HVAC control module operate and provide sufficient heating?

--

Go to Step 3

Go to Too Cold in Vehicle

3

Important:: If during this diagnostic procedure the HVAC control module is disconnected a recalibration of actuators must be performed to avoid misdiagnosis.

  1. Recalibrate actuators. Refer to Actuator Recalibration .
  2. Turn ON the ignition, with the engine OFF.
  3. Observe the current DTC list in Heating and Air Conditioning using the scan tool.

Does the scan tool display DTC B0229, B0414, B0434, B3761 or B3764?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Step 4

4
  1. Turn ON the ignition, with the engine OFF.
  2. Select REAR CNTL on the front auxiliary HVAC control assembly.
  3. Place the auxiliary blower motor switch on the auxiliary HVAC control module in each speed position.

Does the auxiliary blower motor operate at all?

--

Go to Step 5

Go to Auxiliary Blower Motor Inoperative

5

Does the auxiliary blower motor operate at the desired speed for each speed position?

--

Go to Step 6

Go to Auxiliary Blower Motor Malfunction

6

Does the Auxiliary Too Cold in Vehicle concern occur when heating is required?

--

Go to Step 7

Go to Step 9

7
  1. Start the engine.
  2. Place the blower motor switch in the OFF position.
  3. Place the A/C request switch 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:

    • A low coolant level
    • A loose or worn accessory drive belt
    • A leaking radiator hose or auxiliary heater hoses
    • A kinked radiator hose or auxiliary heater hoses
    • A missing radiator cap pressure seal
    • A leaking radiator cap

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. With a scan tool, observe the Aux. Mix Door Actual data parameter in the Auxiliary ECC Data list.
  3. Select REAR CNTL on the front auxiliary HVAC control assembly.
  4. Place the auxiliary air temperature switch on the auxiliary HVAC control module from the coldest to hottest position.

Do the counts change?

--

Go to Step 10

Go to Step 13

10
  1. Select OFF on the front auxiliary HVAC control assembly.
  2. Place the auxiliary air temperature switch on the front auxiliary HVAC control assembly from the coldest to hottest position.

Do the counts change?

--

Go to Step 11

Go to Step 15

11

Place your hand directly over the infrared sensor on the rear auxiliary HVAC control module.

Does the temperature value change?

--

Go to Step 12

Go to Step 21

12
  1. Turn ON the ignition, with the engine OFF.
  2. Observe the Aux. Upper Outlet Temp. and the Aux. Lower Outlet Temp. parameter in the Auxiliary ECC Data list.
  3. Turn OFF the ignition.
  4. Measure the resistance of the upper auxiliary and the lower auxiliary air temperature sensors. Refer to Sensor Resistance Table .
  5. Compare the resistance of the sensor to the count value of the scantool.

Does the resistance measure near the sensor resistance table value?

--

Go to Heating Performance Diagnostic

Go to Step 17

13

Test the 5 volt reference circuit of the front auxiliary HVAC control assembly for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 24

Go to Step 14

14

Test the front auxiliary temperature door control circuit of the front auxiliary HVAC control assembly for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 24

Go to Step 16

15

Test the front auxiliary temperature door control circuit of the front auxiliary HVAC control assembly for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 24

Go to Step 16

16
  1. Measure the resistance from the front auxiliary temperature door control terminal to the low reference terminal on the front auxiliary HVAC control assembly.
  2. Place the front auxiliary air temperature switch from the coldest position to the warmest position.

Does the resistance change?

--

Go to Step 20

Go to Step 19

17

Check the suspect air temperature sensor for proper installation. Refer to Air Temperature Sensor Replacement - Upper Auxiliary or Air Temperature Sensor Replacement - Lower Auxiliary .

Did you find and correct the condition?

--

Go to Step 24

Go to Step 18

18

Inspect for poor connections at the harness connector of the suspect 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 24

Go to Step 21

19

Inspect for poor connections at the harness connector of the front auxiliary HVAC control assembly. 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 24

Go to Step 22

20

Inspect for poor connections at the harness connector of the auxiliary 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 24

Go to Step 23

21

Replace the suspect air temperature sensor. Refer to Air Temperature Sensor Replacement - Upper Auxiliary or Air Temperature Sensor Replacement - Lower Auxiliary .

Did you complete the replacement?

--

Go to Step 24

--

22

Replace the front auxiliary HVAC control assembly. Refer to Auxiliary Heater and Air Conditioning Control Replacement - Front .

Did you complete the replacement?

--

Go to Step 24

--

23

Replace the auxiliary HVAC control module. Refer to Auxiliary Heater and Air Conditioning Control Module Replacement .

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