GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2000 🢒 Firebird 🢒 HVAC 🢒 Heating, Ventilation and Air Conditioning 🢒 HVAC Compressor Clutch Does Not Engage

Step

Action

Value(s)

Yes

No

DEFINITION: A/C compressor clutch will not engage when an A/C request has been made and no Powertrain DTCs are set.

1

Did you perform the Diagnostic System Check?

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Go to Step 2

Go to Diagnostic System Check

2
  1. Turn the ignition switch to the OFF position.
  2. Install both the high and low A/C freon pressure gages.
  3. Read the freon pressure with the engine off.
    4. • Freon pressure in the high and low sides should equal each other after the A/C system has come to rest.
    • Freon pressure will fluctuate depending on ambient temperature.
    • Proper clutch operation depends on correct refrigerant charge. Low freon charge will shut off A/C compressor operation.

Are the high and low side freon pressures below the specified value?

345 kPa (50 psi)

Go to Leak Testing in Heating, Ventilation, and Air Conditioning

Go to Step 3

3

Are the high and low side freon pressures above the specified value?

690 kPa (100 psi)

Go to Step 4

Go to Step 5

4

Evacuate and recharge the A/C system according to proper freon fill specifications.

Has the A/C system been recharged properly?

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Go to Step 24

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5

Test for and repair a short to ground in the supply voltage circuit of the A/C compressor clutch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and repair a short to ground?

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Go to Step 24

Go to Step 6

6
  1. Remove the A/C clutch relay from the engine wiring harness junction block 2.
  2. Disconnect the A/C compressor clutch coil connector.
  3. Connect a fused jumper between the ignition voltage terminal for the switch side of the A/C clutch relay and the engine wiring harness junction block 2 connector C1 terminal F8.
  4. Connect a DMM between the A/C compressor clutch coil connector terminal B and ground.
  5. Turn the ignition switch to the RUN position.
  6. Measure the available voltage at the A/C compressor clutch coil connector terminal B.

Is the voltage the same as the specified value?

B+

Go to Step 8

Go to Step 7

7

Repair a poor connection or an open in the supply voltage circuit of the A/C compressor clutch. Refer to Wiring Repairs or Connector Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 24

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8

Using a DMM, measure for continuity between terminal B of the A/C compressor clutch coil connector and ground.

Is the resistance to ground less than the specified value?

0 - 2 ohms

Go to Step 10

Go to Step 9

9

Repair a poor connection or an open in the ground circuit of the A/C compressor clutch. Refer to Wiring Repairs or Connector Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 24

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10
  1. Disconnect the powertrain control module (PCM) connector C2.
  2. Reinstall the A/C clutch relay.
  3. Connect a fused jumper between the PCM connector C2 terminal 39 and ground.
  4. Turn the ignition switch to the RUN position.
  5. Using a DMM, measure the voltage between the A/C compressor clutch coil connector terminal B and ground.

Is the voltage the same as the specified value?

B+

Go to Step 11

Go to Step 12

11
  1. Remove the fused jumper from the PCM connector C2 terminal 39 and ground.
  2. Reconnect the A/C compressor clutch coil connector.
  3. Reinstall the fused jumper between the PCM connector C2 terminal 39 and ground.
  4. Turn the ignition switch to the ON position.

Does the A/C compressor clutch engage?

--

Go to Cooling Insufficient - Air Conditioning (A/C) System in Heating, Ventilation, and Air Conditioning

Go to Step 23

12
  1. Turn the ignition switch to the OFF position.
  2. Remove the A/C clutch relay.
  3. Using a DMM, measure for continuity between the PCM connector C2 terminal 39 and the engine wiring harness junction block 2 connector C1 terminal F7.

Is there continuity?

--

Go to Step 14

Go to Step 13

13

Repair a poor connection or an open in the control circuit of the A/C clutch relay. Refer to Wiring Repairs or Connector Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 24

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14

Replace the A/C clutch relay and retest the A/C system. Refer to Compressor Relay Replacement in Heating, Ventilation, and Air Conditioning.

Does replacing the A/C clutch relay correct the concern?

--

Go to Step 24

Go to Step 15

15
  1. Disconnect the heater-A/C control connector C2.
  2. Connect a DMM between the PCM connector C2 terminal 22 and the heater-A/C control connector C2 terminal B.
  3. Measure the A/C request signal circuit for resistance between these two connectors.

Is the A/C request signal circuit resistance between the specified values?

0 - 2 ohms

Go to Step 17

Go to Step 16

16

Repair a poor connection or an open in the A/C request signal circuit. Refer to Wiring Repairs or Connector Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 24

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17
  1. Connect a DMM between the PCM connector C2 terminal 22 and ground.
  2. Measure the A/C request signal circuit for continuity to ground.

Is the A/C request signal circuit continuous to ground?

--

Go to Step 18

Go to Step 19

18

Repair a short to ground in the A/C request signal circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 24

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19
  1. Disconnect the DMM.
  2. Reconnect all connectors back to their respective modules.
  3. Install the scan tool to the diagnostic link connector.
  4. Start the engine and allow it to idle in park.
  5. Select the area of the scan tool which will read HVAC button output status.
  6. Depress the A/C button on/off several times.

Does the scan tool read the A/C request being sent by the HVAC control head?

--

Go to Step 20

Go to Step 22

20

Test for and repair a poor connection at the PCM and at the engine wiring harness junction block 2. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 24

Go to Step 21

21

Replace the PCM. Refer to Powertrain Control Module Replacement/Programming (V6) or Powertrain Control Module Replacement/Programming (V8) in Engine Controls.

Did you complete the replacement?

--

Go to Step 24

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22

Replace the heater-A/C control. Refer to Control Assembly Replacement .

Did you complete the replacement?

--

Go to Step 24

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23

Replace the A/C compressor clutch coil. Refer to Compressor Clutch Coil Removal (V5 - Conventional Mount) and Compressor Clutch Coil Install (V5 - Conventional Mount) (V6) or Compressor Clutch Coil Removal (V7 - Direct Mount) and Compressor Clutch Coil Install (V7 - Direct Mount) (V8).

Did you complete the replacement?

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Go to Step 24

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24

Operate the system in order to verify the repair.

Did you correct the condition?

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System OK

Go to Step 3