Unit Service; Diverter Doors; Main Hvac Unit - Hummer H1 Service Manual

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UNIT SERVICE

WARNING: When working with refrigerant, always
use protective equipment to prevent injury. Refrigerant
handling should be done only by technicians trained
and certified in the use of refrigerant and refrigerant
service equipment.
CAUTION: Use only equipment and materials designed to op-
erate with R134a refrigerant. Never substitute parts or materi-
als designed for R12.
CAUTION: Never use sealers in or on the HVAC unit that are
not designed for ventilation systems. Some sealers release nox-
ious or irritating odors that will be offensive to operators of the
vehicle. Neutral cure sealers should be used when sealing any
area of the HVAC unit that could potentially expose the opera-
tor of the vehicle or the passengers to the released chemicals.

MAIN HVAC UNIT

The main HVAC unit is comprised of a heater core for heating
air, and evaporator for cooling air, mode doors to direct air-
flow, and an electric blower motor and fan to force air through
the case to be heated or cooled, then directed to the selected
zones in the vehicle (Figure 11-56).
FACE OUTLET
MAIN HVAC UNIT
DRAIN TUBE
Figure 11-56: Main HVAC Unit
05745159
Heating/Ventilation/Air Conditioning (HVAC)

Diverter Doors

Four diverter doors occupy the outlet area of the main unit.
Various positions and combinations of 4 doors provide the sys-
tem with the following mode selections:
All 5 of the mode doors are operated using vacuum door mo-
tors mounted externally to the case (Figure 11-57). The motors
are as follows:
The vacuum motors are capable of 2 positions: fully extended
(spring pressure), or fully retracted (vacuum). The face door
motor is an exception, having a third position in the middle of
VACUUM MOTOR
travel. A second vacuum inlet is added to the face door motor
COVER
for this purpose (Figure 11-57).
The temperature blend door motor operates the temperature
blend door. This door is responsible for regulating outlet air
temperature by directing air through the heater core or by
blocking air to the core. The temperature blend door motor is
electric, and can be positioned at multiple positions.
DEFROST
BLOCKOFF
MOTOR
FACE DOOR MOTOR
7-P11-001
TEMPERATURE BLEND DOOR
7-P11-001.4
• Off
• Maximum A/C - Recirculate
• A/C
• A/C Face/Floor blend
• Face
• Floor
• Defrost/Floor blend
• Defrost
• Floor door motor
• Defrost blockoff motor
• Face door motor
• Defrost door motor
• Recirculate door motor
7-S11-031
RECIRCULATE DOOR MOTOR
Figure 11-57: Vacuum Door Motors
11-37
FLOOR DOOR MOTOR
DEFROST DOOR
MOTOR