GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2003 🢒 Corvette 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 Air Delivery Improper

Test Description

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

  1. Test the HVAC control module front defrost button and the mode button for proper operation.

    2.

  2. Can you hear the recirculation door switch from outside air to the recirculation position.

    3.

  3. Tests the HVAC control module for the proper commanded state. The ON/OFF positions for each mode are as follows:

    FLOOR POSITION -- solenoids 1 and 5 OFF, solenoids 2 and 3 ON, solenoid 4 ON or OFF.

    VENT POSITION -- solenoids 1 and 3 OFF, solenoids 2 and 5 ON, solenoid 4 ON or OFF.

    VENT/FLOOR POSITION -- solenoids 1, 3 and 5 OFF, solenoid 2 ON, solenoid 4 ON or OFF.

    FLOOR/DEFROST POSITION -- solenoids 1, 2, 4 and 5 OFF and solenoid 3 ON.

    DEFROST POSITION -- solenoids  1 and 3 ON and solenoids 2, 4 and 5 OFF.

    4.

  4. Tests the solenoid circuits for an open or short.

    5.

  5. Tests the solenoid circuits for an open or short.

    6.

  6. Tests the vacuum control assembly solenoids.

    7.

  7. Tests for a constant ground, constant voltage and an open on the solenoid control circuits.

Step

Action

Values

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

DEFINITION: Air does not flow correctly from the air distribution outlets.

1

Did you perform the HVAC Diagnostic System Check?

--

Go to Step 2

Go Diagnostic System Check - HVAC Systems - Automatic to

2
  1. Start the engine.
  2. Place the blower motor switch in the OFF position.

Is the blower motor OFF?

--

Go to Step 3

Go to Blower Motor Always On

3

Place the blower motor switch in each speed position.

Does the blower motor operate in any of the speed positions?

--

Go to Step 4

Go to Blower Motor Inoperative

4

Does the blower motor operate at the desired speed in each speed position?

--

Go to Step 5

Go to Blower Motor Malfunction

5

  1. Install a scan tool.
  2. With a scan tool, observe the Mode Button parameter in the Heating and Air Conditioning data list.
  3. Activate the mode switch.
  4. With a scan tool, observe the Front Defrost Button parameter in the Heating and Air Conditioning data list.
  5. Activate the front defrost switch.

Does the scan tool indicate that both the Mode Button and Front Defrost Button parameters change state?

--

Go to Step 6

Go to Step 15

6

  1. Place the blower motor switch in the maximum speed position.
  2. Place the mode switch in the vent position.
  3. Place the outside air switch in the OFF position.
  4. Place the recirculation switch in the ON position.

Does the recirculation door operate properly?

--

Go to Step 7

Go to Air Recirculation Malfunction

7

  1. Place the mode switch in each mode position.
  2. Place the defrost switch in the defrost position.

Does the air flow from the correct air distribution outlets in each mode position?

--

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 8

8

  1. Install a scan tool.
  2. With a scan tool, observe the Vacuum Solenoid parameters in the Heating and Air Conditioning data list.
  3. Place the mode switch in each position.

Does the scan tool indicate that each observed solenoid parameter changes to ON when the corresponding mode is activated?

--

Go to Step 9

Go to Step 15

9

  1. Turn OFF the ignition.
  2. Disconnect the vacuum control assembly.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the ignition 3 voltage circuit of the vacuum control assembly with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 10

Go to Step 16

10

  1. Place the mode switch in the VENT position.
  2. Place the RECIRC air switch in the RECIRCULATION position.
  3. Measure the voltage between the ignition 3 voltage circuit and solenoid circuits 1, 2, 3, 4 and 5 of the vacuum control assembly connector.

Does solenoid circuits 1 and 3 measure 0 volts and solenoids 2, 4 and 5 measure 12 volts?

--

Go to Step 11

Go to Step 13

11

  1. Place the DEFROST switch in the DEFROST position.
  2. Measure the voltage between the ignition 3 voltage circuit and solenoid circuits 1, 2, 3, 4 and 5 of the vacuum control assembly connector.

Does solenoid circuits 1 and 3 measure 12 volts and solenoids 2, 4 and 5 measure 0 volts?

--

Go to Step 12

Go to Step 13

12

  1. Remove the vacuum control assembly.
  2. Measure the resistance between the ignition 3 voltage circuit pin and solenoid circuit pins 1, 2, 3, 4 and 5 of the vacuum control assembly.

Is the resistance for each solenoid between the specified value?

70 to 110 ohms

Go to Vacuum Control System Diagnostic

Go to Step 14

13

Test the appropriate control circuit for an open, short to ground or short to voltage. Refer to Circuit Testing in Wiring Systems.

Did you find and correct the condition?

12 V

Go to Step 19

Go to Step 15

14

Inspect for poor connections at the harness connector of the vacuum 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 19

Go to Step 17

15

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 19

Go to Step 18

16

Repair the ignition 3 voltage circuit of the vacuum control assembly for an open or high resistance. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 19

--

17

Replace the vacuum control assembly. Refer to Vacuum Control Assembly Replacement .

Did you complete the replacement?

--

Go to Step 19

--

18

Replace the HVAC control module. Refer to HVAC Control Module Replacement .

Did you complete the replacement?

--

Go to Step 19

--

19

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2