GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2004 🢒 Regal 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 Air Delivery Improper

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. Observe the Vacuum Solenoid parameters to verify that the appropriate solenoids are energized for their respective modes. In Vent mode, solenoid 3 is ON. In Defrost mode, solenoids 1 and 3 are ON--Please note that the Defrost switch should be activated in this mode. In Vent/Recirc, solenoids 3 and 4 are ON--Note that the Recirc switch should be activated in this mode. In Heater mode, solenoids 2 and 3 are ON. In Recirc mode solenoids 2, 3, and 4 are ON. In Def/Heater mode, solenoids 2 and 5 are ON.

    2.

  2. Test the solenoid control circuit of the solenoid that does not click ON and OFF. Verifies that the HVAC control module is providing ground to the solenoid in the vacuum control assembly.

    3.

  3. Tests if ground is constantly being applied to the vacuum control assembly.

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

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 ON 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 Vacuum Control System Diagnostic

Go to Step 9

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. Measure the voltage between the ignition 3 voltage circuit of the vacuum control assembly and the applicable solenoid control circuit of the vacuum control assembly.
  2. Place the mode switch in the applicable mode position and then OFF.

Does the voltage measure near the specified values for each commanded state?

12 V ON

0 V OFF

Go to Step 14

Go to Step 11

11

Does the voltage remain near the specified value with each command?

12 V

Go to Step 13

Go to Step 12

12

Test the appropriate solenoid control circuit of the vacuum control assembly for a short to voltage or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 15

13

Test the appropriate solenoid control circuit of the vacuum 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 19

Go to Step 14

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 Wiring Repairs to 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