GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

DEFINITION: The A/C compressor clutch will not engage when an A/C request has been made and a Powertrain DTC has not been set.

1

Did you perform the Diagnostic System Check - Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Start the engine.
  2. Place the blower motor switch in the maximum speed position.
  3. Ensure the A/C OFF switch is not selected.
  4. Place the left air temperature switch in the coldest position.

Does the A/C compressor operate?

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Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 3

3

  1. Start the engine.
  2. Observe the coolant temperature indicator.

Is the engine coolant temperature indicator illuminated?

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Go to Diagnostic System Check - Vehicle

Go to Step 4

4

  1. Turn OFF the ignition.
  2. Install the ACR 2000.
  3. Record the ambient temperature at the vehicle.
  4. Record readings of the low and high side STATIC pressures.
  5. Compare the low and the high side pressure values with the allowable limits for the recorded ambient air temperature.

Are the low and the high side pressure values within the allowable limits for the recorded ambient air temperature and are the pressure values within 103 kPa (15 psi) of each other?

Above 16°C (60°F) 345 kPa (50 psi)

Above 24°C (75°F) 483 kPa (70 psi)

Above 33°C (90°F) 690 kPa (100 psi)

Go to Step 5

Go to Leak Testing

5

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool observe the A/C refrigerant pressure sensor in the engine control module (ECM) data list.
  4. Compare the A/C refrigerant pressure sensor parameter on the scan tool with the ACR 2000 high side pressure value.

Is the scan tool A/C refrigerant pressure sensor parameter and the ACR 2000 pressure value within 15 psi of each other?

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Go to Step 6

Go to Step 14

6

With a scan tool, view the evaporator temperature in the HVAC system data.

Is the evaporator temperature below 4°C (39°F)?

--

Go to Step 17

Go to Step 7

7

With a scan tool, view the ambient air temperature in the HVAC system data.

Is the ambient air temperature below 3°C (38°F)?

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Go to Step 18

Go to Step 8

8

  1. Turn OFF the ignition.
  2. Disconnect the A/C compressor clutch.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the supply voltage circuit of the A/C compressor clutch with a test lamp that is connected to ground.
  5. With a scan tool, command the A/C compressor clutch relay ON.

Does the test light illuminate?

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Go to Step 9

Go to Step 10

9

Test the ground circuit of the A/C compressor clutch for a high resistance or for an open. Refer to Circuit Testing and to Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 29

Go to Step 13

10

Test the voltage supply circuit of the A/C compressor clutch for a high resistance or for an open. Refer to Circuit Testing and to Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 29

Go to Step 11

11

  1. Turn OFF the ignition.
  2. Disconnect the A/C compressor clutch relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the battery positive voltage circuit of the A/C compressor clutch relay with a test lamp that is connected to ground.

Does the test light illuminate?

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Go to Step 12

Go to Step 25

12

Inspect for poor connections at the A/C compressor clutch relay. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs .

Did you find and correct the condition?

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Go to Step 29

Go to Step 26

13

Inspect for poor connections at the A/C compressor clutch relay. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs .

Did you find and correct the condition?

--

Go to Step 29

Go to Step 27

14

  1. Disconnect the A/C pressure sensor.
  2. With a test lamp connected to battery voltage, probe the ground circuit at the A/C pressure sensor connector.

Does the test light illuminate?

--

Go to Step 19

Go to Step 15

15

Test the ground circuit of the A/C refrigerant pressure sensor for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 29

Go to Step 16

16

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 29

Go to Step 28

17

Inspect the evaporator temperature sensor circuits for high resistance. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 29

Go to Step 21

18

Inspect the ambient air temperature sensor circuits for high resistance. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 29

Go to Step 22

19

Inspect for poor connections at the harness connector of the A/C pressure sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 29

Go to Step 20

20

Replace the A/C refrigerant pressure sensor.

Have you finished the replacement?

--

Go to Step 29

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21

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

Did you find and correct the condition?

--

Go to Step 29

Go to Step 23

22

Inspect for poor connections at the harness connector of the ambient 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 29

Go to Step 24

23

Replace the evaporator temperature sensor. Refer to Auxiliary Temperature Valve Actuator Replacement .

Have you finished the replacement?

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Go to Step 29

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24

Replace the ambient air temperature sensor. Refer to Ambient Air Temperature Sensor Replacement .

Have you finished the replacement?

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Go to Step 29

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25

Repair the battery positive voltage circuit of the A/C compressor clutch relay. Refer to Wiring Repairs .

Is the trouble corrected?

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Go to Step 29

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26

Replace the A/C compressor clutch relay.

Have you finished the replacement?

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Go to Step 29

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27

Replace the A/C compressor clutch. Refer to Air Conditioning Compressor Replacement .

Have you finished the replacement?

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Go to Step 29

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28

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

Have you finished the replacement?

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Go to Step 29

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29

Operate the system to verify the repair.

Did you correct the condition?

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System OK

Go to Step 2