GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2001 🢒 Eldorado 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 Air Recirculation Malfunction

Test Description

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

  1. Listen for an audible click or feel for the click when the vacuum control assembly operates. Repeat the test as necessary.

    2.

  2. Tests for voltage at the vacuum control assembly.

    3.

  3. Verifies that the HVAC control processor is providing ground to the vacuum control assembly.

    4.

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

Step

Action

Value(s)

Yes

No

Schematic Reference: HVAC Schematics

DEFINITION: Air recirculation is inoperative or always ON.

1

Did you perform the HVAC Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Automatic

2
  1. Start the engine
  2. Place the blower motor switch in the maximum speed position.
  3. Place the mode switch in the vent position.
  4. Place the recirculation switch in the ON and OFF positions.

Does the recirculation door operate properly?

--

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

Go to Step 3

3

  1. Install a scan tool.
  2. With a scan tool, command the recirculation mode valve solenoid ON and OFF.

Does the recirculation mode valve solenoid turn ON and OFF?

--

Go to Vacuum Control System Diagnostic

Go to Step 4

4

  1. Turn OFF the ignition.
  2. Disconnect the vacuum control assembly.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the vacuum control assembly supply 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 5

Go to Step 9

5

  1. Measure the voltage between the vacuum control assembly supply voltage circuit of the vacuum control assembly and the recirculation mode valve solenoid control circuit of the vacuum control assembly.
  2. With a scan tool, command the recirculation mode valve solenoid ON and OFF.

Does the measured voltage change between the specified values?

0-12 V

Go to Step 10

Go to Step 6

6

Does the measured voltage remain near the specified value?

12 V

Go to Step 8

Go to Step 7

7

Test the recirculation mode valve 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 14

Go to Step 11

8

Test the recirculation mode valve 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 14

Go to Step 11

9

Test the vacuum control assembly supply voltage circuit of the vacuum control assembly for an open, high resistance or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 11

10

Inspect for poor connections at 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 14

Go to Step 12

11

Inspect for poor connections at the harness connector of the HVAC control processor. 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 14

Go to Step 13

12

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

Did you complete the replacement?

--

Go to Step 14

--

13

Replace the HVAC control processor. Refer to HVAC Control Processor Replacement .

Did you complete the replacement?

--

Go to Step 14

--

14

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 3