HVAC Compressor Clutch Does Not Engage. HUMMER H3 2007

For 1990-2009 cars only

Makes 🢒 HUMMER 🢒 2007 🢒 H3 🢒 HVAC 🢒 HVAC - Manual 🢒 HVAC Compressor Clutch Does Not Engage

Diagnostic Aids

The air conditioning (A/C) compressor clutch will not engage under the following conditions:

•	The A/C high side line pressure is over 2 413 kPa (350 psi).

•	Throttle angle is at 100 percent.

•	Engine speed is more than 5,500 RPM.

•	Engine coolant temperature (ECT) is more than 123°C (253°F).

•	Evaporator core temperature is less than 0°C (32°F).

•	The powertrain control module (PCM) minimum OFF time to engage the compressor is 7-9 seconds. The scan tool, A/C Relay Command Delay, body control module (BCM) Inputs data list, can validate this.

•	The evaporator temperature sensor is normally closed. The evaporator temperature sensor opens at 0°C (32°F).

Test Description

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

The A/C compressor relay output is disabled if the ECT is above 124°C (255°F). The Check Gages indicator will illuminate at this temperature and the driver information center (DIC) will display the ENG HOT message.

These actions will enable the A/C compressor to operate.

This test ensures that there is sufficient refrigerant in the A/C system. The specific values come from the A/C System Performance Test.

If an audible click is heard when the 10-amp is installed then the answer is yes.

Checks the function of the thermistor of the evaporator temperature sensor. The thermistor and module side of the harness are located behind the glove box.

Checks the resistance of the 2 gray wires at the evaporator temperature sensor module behind the glove box. As the evaporator gets colder the evaporator circuit resistance goes up.

Checks the resistance of the 2 gray wires running out of the evaporator temperature sensor itself located at the evaporator core which is contained within the HVAC module or HEBA. As the evaporator gets colder the evaporator circuit resistance goes up.

If the OFF blower motor control circuit is shorted to ground, the output of the HVAC control module for an A/C request is disabled.

Step

Action

Values

Yes

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.

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

Start the engine.
Observe the driver information center (DIC) message center.

Does the DIC display the ENG HOT message?

Go to Engine Overheating

Go to Step 3

Important: For air conditioning (A/C) compressor operation, the evaporator core temperature must be above 0°C (32°F).

Start the engine.
Place the blower motor switch in the low speed position.
Place the A/C request switch to the ON position.

Does the A/C compressor clutch engage?

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 4

Turn OFF the ignition.
Turn ON the ignition, with the engine OFF.
With a scan tool, observe the A/C Request Signal parameter in the body control module (BCM) inputs data list.
Place the A/C request switch to the ON position.

Does the scan tool indicate that the A/C Request Signal parameter displays Yes?

Go to Step 5

Go to Step 11

Park the vehicle inside or out of direct sunlight.
Open the window in order to ventilate the interior of the vehicle.
Turn OFF the ignition.
If the A/C system was operating, then wait for approximately 2 minutes.
Install J 43600 ACR 2000 Air Conditioning Service Center.
Record the ambient temperature at the vehicle.
Record readings of the low and high side STATIC pressures.
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. 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 6

Go to Leak Testing

Disconnect the A/C compressor relay.
Probe the battery positive voltage circuit of the A/C compressor clutch relay with a test lamp connected to a good ground.

Does the test lamp illuminate?

Go to Step 7

Go to Step 18

Connect a 10-amp fused jumper between the battery positive voltage circuit and the A/C compressor clutch supply voltage circuit of the A/C compressor clutch relay.

Does the A/C compressor clutch engage?

Go to Step 19

Go to Step 13

Important: Access the evaporator temperature sensor gray control circuits and module with 2-way connector to BCM and HVAC control module behind the glove box.

Disconnect the evaporator temperature sensor at the 2-wire connector running from the evaporator temperature control circuits to the HVAC control module and BCM behind the glove box.
Connect a test light between the A/C request circuit of the HVAC control module and the BCM at the 2-wire connector of the evaporator temperature sensor.

Does the A/C compressor engage?

Go to Step 9

Go to Step 11

Important: Access the evaporator temperature sensor gray control circuits and module with 2-way connector to BCM and HVAC control module behind the glove box.

With a 3-amp fused jumper attached between the BCM and the HVAC control module A/C request circuits at the 2-wire evaporator temperature sensor behind the glove box.
Check the resistance of the 2 gray evaporator temperature sensor circuits at the evaporator temperature sensor behind the glove box.
Start the engine.

Does the resistance value stay within the specified value range even after compressor engagement?

Temperature Minimum 14.9°C (58.82°F) - Resistance Minimum 15651 ohms

Temperature Maximum 30.1°C (86.18°F) - Resistance Maximum 8190 ohms

Go to Step 25

Go to Step 10

Important: Access the evaporator temperature sensor gray control circuits and module with 2-way connector to BCM and HVAC control module behind the glove box.

With a 3-amp fused jumper attached between the BCM and the HVAC control module A/C request circuits at the 2-wire evaporator temperature sensor behind the glove box.
Cut the 2 gray evaporator temperature sensor circuits no less than 2 inches from the evaporator temperature sensor module behind the glove box.
Start the engine.
Check the resistance of the 2 gray wires at the evaporator temperature sensor coming out of the evaporator core at the HVAC module.

Does the resistance value move from the specified value range when the compressor is engaged?

Temperature Minimum 14.9°C (58.82°F) - Resistance Minimum 15651 ohms

Temperature Maximum 30.1°C (86.18°F) - Resistance Maximum 8190 ohms

Go to Step 25

Go to Step 26

Important: Access the evaporator temperature sensor control circuits and module through the glove box.

Disconnect the evaporator temperature sensor at the 2-wire pinout running to the HVAC control module behind the radio.
Probe the A/C request signal circuit of the HVAC control module with a DMM connected to a good ground.

Does the DMM indicate at least the specified value?

12 V

Go to Step 12

Go to Step 15

Connect a 3-amp fused jumper between the A/C request signal circuit of the HVAC control module and the A/C request signal circuit of the BCM.
Observe the A/C Request Signal parameter.

Does the scan tool indicate the A/C Request Signal parameter is Yes?

Go to Step 20

Go to Step 17

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

Did you find and correct the condition?