Hummer H2. Manual — part 1959

Fig. 39: Sun Load Sensor & I/P Upper Trim Pad
Courtesy of GENERAL MOTORS CORP.

1. Remove the I/P upper trim pad. Refer to Trim Pad Replacement - Instrument Panel (I/P) Upper in

Trim Pad Replacement-I/P Upper.

2. Remove the sun load sensor from the I/P upper trim pad by turning counter clockwise.

3. Disconnect the electrical connector from the sun load sensor.

Installation Procedure

2004 Hummer H2

2004 HVAC HVAC Systems - Automatic - Hummer H2

Fig. 40: Sun Load Sensor & I/P Upper Trim Pad
Courtesy of GENERAL MOTORS CORP.

1. Connect the electrical connector to the sun load sensor.

2. Install the sun load sensor to the I/P upper trim pad by turning clockwise.

3. Install the I/P upper trim pad. Refer to Trim Pad Replacement - Instrument Panel (I/P) Upper .

DESCRIPTION AND OPERATION

2004 Hummer H2

2004 HVAC HVAC Systems - Automatic - Hummer H2

AIR DELIVERY DESCRIPTION AND OPERATION

The air delivery description and operation is divided into 5 areas:

z

HVAC Control Components

z

Air Speed

z

Air Delivery

z

Recirculation Operation

z

Automatic Operation

HVAC Control Components

HVAC Control Module

The HVAC control module is a class 2 device that interfaces between the operator and the HVAC system to
maintain air temperature and distribution settings. The battery positive voltage circuit provides power that the
control module uses for keep alive memory (KAM). If the battery positive voltage circuit loses power, all
HVAC DTCs and settings will be erased from KAM. The body control module (BCM), which is the vehicle
mode master, provides a device on signal. The control module supports the following features:

Air Delivery Description and Operation

Mode Actuator

The mode actuator is a 5 wire bi-directional electric motor that incorporates a feedback potentiometer. Ignition
3 voltage, low reference, control, 5-volt reference and position signal circuits enable the actuator to operate. The
control circuit uses either a 0, 2.5 or 5 volt signal to command the actuator movement. When the actuator is at
rest, the control circuit value is 2.5 volts. A 0 or 5 volt control signal commands the actuator movement in
opposite directions. When the actuator shaft rotates, the potentiometer's adjustable contact changes the door
position signal between 0-5 volts.

The HVAC control module uses a range of 0-255 counts to index the actuator position. The door position signal
voltage is converted to a 0-255 count range. When the module sets a commanded, or targeted, value, the control
signal is changed to either 0 or 5 volts depending upon the direction that the actuator needs to rotate to reach the
commanded value. As the actuator shaft rotates the changing position signal is sent to the module. Once the
position signal and the commanded value are the same, the module changes the control signal to 2.5 volts.

Blower Motor Control Processor

The blower motor control processor controls the speed of the blower motor by increasing or decreasing the

Feature

Availability

Afterblow

No

Purge

No

Personalization

Yes

Actuator Calibration

Yes

2004 Hummer H2

2004 HVAC HVAC Systems - Automatic - Hummer H2

voltage drop on the ground side of the blower motor. The HVAC control module provides a linear pulse
modulated signal to the blower motor control processor over the blower motor speed control circuit. As the
requested blower speed increases, the HVAC control module increases the amount of time that the speed signal
is modulated to ground. As the requested blower speed decreases, the HVAC control module decreases the
amount of time that the signal is modulated to ground.

Air Speed - Front Control

The blower control switch is integrated into the HVAC control module. The two rocker type switches provide
the vehicle operator the ability to select several blower speeds. The HVAC control module uses a bar graph type
display to indicate the selected blower speed. The HVAC control module provides a linear pulse modulated
(LPM) signal to the blower motor through the blower motor speed control circuit. The blower motor changes
speed based on the received LPM signal from the HVAC control module. Power and ground are provided to the
blower motor through the battery positive voltage and ground circuits. When the HVAC control module is
operating in AUTO mode, the system automatically controls the blower speed. Power and ground are provided
to the HVAC control module by the ignition 3 voltage and the ground circuits.

Air Distribution

The HVAC control module controls the distribution of air by the use of a mode actuator. The modes that may
be selected are:

z

Defrost

z

Defog

z

Panel

z

BI-Level

z

Floor

Mode Actuator

The mode actuator is connected to the mode door by a cam type linkage system. Depending on the position of
the door, air is directed through the HVAC module and distributed through various ducts leading to the outlets
in the dash. If the HVAC control module detects a fault with the mode door the HVAC control module will try
to drive the actuator for a predetermined amount of time, to defrost, which is the defaulted position for the mode
door actuator. When the mode switch is placed in the defrost or defog positions the A/C is commanded ON and
the recirculation door is moved to the outside air position to help reduce window fogging. A/C is available in all
modes and recirculation is only available in the panel and bi-level modes.

Front Defrost

When defrost is selected, the A/C compressor is activated. The A/C compressor clutch will engage when
ambient temperatures are above 3° C (38° F). The blower motor will be activated, regardless of the coolant
temperature. The HVAC control module will override the auxiliary HVAC control module so a high volume of
air is delivered to the front defrost vents. The rear window defogger does not affect the HVAC system.

Recirculation Operation

2004 Hummer H2

2004 HVAC HVAC Systems - Automatic - Hummer H2