Jeep 1996 Grand Cherokee Service Manual - page 1393
GENERAL INFORMATION
HEATER AND AIR CONDITIONER
A manual temperature control type heating-air
conditioning system is standard factory-installed
equipment on this model. An electronically controlled
Automatic Temperature Control (ATC) type heating-
air conditioning system is an available factory-in-
stalled option.
All vehicles are equipped with a common heater-
A/C housing assembly (Fig. 1). The system combines
air conditioning, heating, and ventilating capabilities
in a single unit housing mounted under the instru-
ment panel.
Outside fresh air enters the vehicle through the
cowl top opening at the base of the windshield, and
passes through a plenum chamber to the heater-A/C
system blower housing. Air flow velocity can then be
adjusted with the blower motor speed selector switch
on the heater-A/C control panel. The air intake open-
ings must be kept free of snow, ice, leaves, and other
obstructions for the heater-A/C system to receive a
sufficient volume of outside air.
The heater-air conditioner is a blend-air type sys-
tem. In a blend-air system, a blend-air door controls
the amount of cooled or unconditioned air is allowed
to flow through, or around, the heater core. A temper-
ature control knob on the heater-A/C control panel
determines the discharge air temperature by actuat-
ing the blend-air door. This allows an almost imme-
diate control of the system’s output air temperature.
The mode control knob on the heater-A/C control
panel is used to direct the conditioned air to the
selected system outlets. On manual temperature con-
trol systems, the mode control knob switches engine
vacuum to control the mode doors, which are oper-
ated by vacuum actuator motors. On ATC systems,
the mode control knob switches electrical current to
control the mode doors, which are operated by elec-
tronic actuator motors.
The outside air intake can be shut off by selecting
the recirculation mode with the mode control knob.
This will open the recirculating air door and recircu-
late the air that is already inside the vehicle.
The air conditioner for all models is designed for
the use of non-CFC, R-134a refrigerant. The air con-
ditioning system has an evaporator to cool and dehu-
midify the incoming fresh or recirculated air prior to
blending it with the heated air. This system uses a
fixed orifice tube in the condenser outlet line to
meter refrigerant flow to the evaporator coil. To
maintain minimum evaporator temperature, a fixed
pressure setting switch on the accumulator cycles the
compressor clutch.
HEATER AND AIR CONDITIONER CONTROLS
The manual temperature control heater-A/C sys-
tem uses a combination of electrical, and vacuum
controls. The ATC heater-A/C system uses only elec-
trical controls. These controls provide the vehicle
operator with a number of setting options to help
control the climate and comfort within the vehicle.
Refer to the Owner’s Manual for more information on
the suggested operation and use of these controls.
Both heater-A/C control panels are located to the
right of the instrument cluster on the instrument
panel (Fig. 2). Both control panels have a tempera-
ture control knob, a mode control knob, a blower
motor switch knob, and an A/C push-button switch.
The ATC control panel includes a Recirc push-button
switch and a vacuum fluorescent display area.
Fig. 1 Common Blend-Air Heater-Air Conditioner
System
Fig. 2 Heater-Air Conditioner Control Panels
24 - 2
HEATING AND AIR CONDITIONING
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