Hummer H3. Manual — part 1291

SYMPTOMS - HVAC SYSTEMS - MANUAL

Visual/Physical Inspection

Inspect for aftermarket devices which could affect the operation of the HVAC System.
Refer to Checking Aftermarket Accessories .

Inspect the easily accessible or visible system components for obvious damage or conditions
which could cause the symptom.

Verify the A/C compressor clutch turns freely and is not seized.

The A/C compressor will not operate in cold outside air temperatures. Refer to Air
Temperature Description and Operation.

The following conditions may cause window fogging:

Wet carpet or mats

High humidity

Interior water leak

Blocked A/C evaporator drain tube

Maximum passenger capacity

Blocked body pressure relief valves

Inspect the air distribution system for causes of reduced air flow:

Obstructed or dirty passenger compartment air filter, if equipped

Blocked or damaged air inlet or outlet vents

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to
Testing for Intermittent Conditions and Poor Connections .

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the
symptom:

IMPORTANT: Review the system operation in order to familiarize yourself with

the system functions. Refer to the following:

Air Delivery Description and Operation

Air Temperature Description and Operation

2007 Hummer H3

2007 HVAC HVAC - Manual - H3

Air Conditioning Compressor Malfunction

Blower Motor Malfunction

Too Hot in Vehicle

Too Cold in Vehicle

Air Delivery Improper

Air Recirculation Malfunction

Leak Testing

Defrosting Insufficient

Noise Diagnosis - Blower Motor

Noise Diagnosis - Air Conditioning (A/C) System

Noise Diagnosis - HVAC Module

Odor Diagnosis

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.

2: 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.

2007 Hummer H3

2007 HVAC HVAC - Manual - H3

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

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

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

8: 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.

9: 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.

10: 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.

16: 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.

HVAC Compressor Clutch Does Not Engage

Step

Action

Values

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?

-

Go to Step 2

Go to
Diagnostic
System
Check -
Vehicle

2

1. Start the engine.

2. 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°

2007 Hummer H3

2007 HVAC HVAC - Manual - H3

3

1. Start the engine.

2. Place the blower motor

switch in the low speed
position.

3. Place the A/C request switch

to the ON position.

Does the A/C compressor clutch
engage?

F).

-

Go to Testing
for
Intermittent
Conditions
and Poor
Connections Go to Step 4

4

1. Turn OFF the ignition.

2. Turn ON the ignition, with

the engine OFF.

3. With a scan tool, observe the

A/C Request Signal
parameter in the body control
module (BCM) inputs data
list.

4. 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

1. Park the vehicle inside or out

of direct sunlight.

2. Open the window in order to

ventilate the interior of the
vehicle.

3. Turn OFF the ignition.

4. If the A/C system was

operating, then wait for
approximately 2 minutes.

5. Install J 43600 ACR 2000

Air Conditioning Service
Center.

Above

16°C

(60°F)

345 kPa

(50 psi)

2007 Hummer H3

2007 HVAC HVAC - Manual - H3