Jeep 1996 Grand Cherokee Service Manual - page 1397
BLOWER MOTOR SWITCH
The heater-A/C blower motor is controlled by a
rotary switch, mounted in the heater-A/C control
panel. On vehicles with manual temperature control
systems, the switch allows the selection of four
blower motor speeds, but will only operate with the
ignition switch in the On position, and the heater-
A/C mode control switch in any position except Off.
On vehicles with ATC systems, the switch allows the
selection of Lo Auto, Hi Auto, and an infinite number
of manual speed settings between Lo and Hi.
On
manual
temperature
control
systems,
the
blower motor switch is connected in series with the
blower motor ground circuit through the heater-A/C
mode control switch. The blower motor switch directs
this ground path to the blower motor through the
blower motor resistor wires, or directly to the blower
motor, as required to achieve the selected blower
motor speed.
On ATC systems, the blower motor switch is just
one of many inputs to the ATC controller. In the
manual blower modes, the ATC controller adjusts the
blower motor speed through the power module or the
high speed blower motor relay as required by the
blower switch position. In the auto blower modes, the
ATC controller it is selected with the blower adjusts
the blower motor speed through the power module or
the high speed blower motor relay as required to
achieve and maintain the selected comfort level.
The blower motor switch cannot be repaired and, if
faulty, must be replaced. The switch is serviced only
as a part of the heater-A/C control assembly.
COMPRESSOR
The air conditioning system uses a Nippon Denso
10PA17 fixed displacement compressor on all models.
A label identifying the use of R-134a refrigerant is
located on the compressor. The purpose of the com-
pressor is to compress the low-pressure refrigerant
vapor from the evaporator into a high-pressure, high-
temperature vapor. The compressor is serviced only
as an assembly.
COMPRESSOR CLUTCH
The compressor clutch assembly consists of a sta-
tionary electromagnetic coil, a hub bearing and pul-
ley assembly, and a clutch plate (Fig. 4). The
electromagnetic coil and pulley are retained on the
compressor with snap rings. The clutch plate is
mounted on the compressor shaft and secured with a
bolt.
These components provide the means to engage
and disengage the compressor from the engine ser-
pentine accessory drive belt. When the clutch coil is
energized, it magnetically draws the clutch into con-
tact with the pulley and drives the compressor shaft.
When the coil is not energized, the pulley free-wheels
on the clutch hub bearing, which is part of the pulley.
The compressor clutch and coil are the only serviced
parts on the compressor.
The compressor clutch is controlled by several com-
ponents: the A/C switch on the heater-A/C control
panel, the ATC controller, the low pressure cycling
clutch switch, the high pressure cut-off switch, the
compressor clutch relay, and the Powertrain Control
Module (PCM). The PCM may delay compressor
clutch engagement for up to 30 seconds. Refer to
Group 14 - Fuel System for more information on the
PCM controls.
COMPRESSOR CLUTCH RELAY
The compressor clutch relay is a International
Standards Organization (ISO) micro-relay. The termi-
nal designations and functions are the same as a con-
ventional
ISO
relay.
However,
the
micro-relay
terminal orientation (footprint) is different, current
capacity is lower, and the relay case dimensions are
smaller than on the conventional ISO relay.
The compressor clutch relay is a electro-mechanical
device that switches current to the compressor clutch
coil when the Powertrain Control Module (PCM)
grounds the coil side of the relay. The PCM responds
to inputs from the A/C switch on the heater-A/C con-
trol panel, the ATC controller, the low pressure
cycling clutch switch, and the high pressure cut-off
switches.
The compressor clutch relay is located in the Power
Distribution Center (PDC) in the engine compart-
ment. Refer to the PDC label for relay identification
and location.
CONDENSER
The condenser is located in front of the engine cool-
ing radiator. It is a heat exchanger that allows the
high-pressure refrigerant gas to give up its heat to
the air passing over the condenser fins. This causes
Fig. 4 Compressor Clutch - Typical
24 - 6
HEATING AND AIR CONDITIONING
ZJ
DESCRIPTION AND OPERATION (Continued)