Jeep 1997 Grand Cherokee Service Manual page 1302

8W - 42 - 14
GENERAL INFORMATION
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . 14
DESCRIPTION AND OPERATION
A/C OPERATION—AUTOMATIC TEMPERATURE
CONTROL . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
A/C OPERATION—MANUAL A/C . . . . . . . . . . . . 14
AMBIENT TEMPERATURE SENSOR . . . . . . . . . 15
AUTOMATIC TEMPERATURE CONTROL (ATC)
MODULE . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
AUTOMATIC TEMPERATURE CONTROL (ATC) . 15
BLEND AIR DOOR MOTOR ACTUATOR—
MANUAL A/C-HEATER . . . . . . . . . . . . . . . . . . 15
GENERAL INFORMATION
INTRODUCTION
This section of the wiring diagrams is divided into
two sub-sections; Manual A/C-Heater, and Automatic
Temperature Control (ATC). When referring to the
circuit descriptions or wiring diagrams, ensure that
you use the correct one.
DESCRIPTION AND OPERATION
MANUAL A/C-HEATER
Several fuses supply power for the manual air con-
ditioning/heater system. When the ignition switch is
in the RUN position, it connects circuit A1 from fuse
8 in the Power Distribution Center (PDC) to circuit
A22. Circuit A22 powers circuit F71 through fuse 12
in the junction block. Circuit F71 connects to the A/C
control switches and the blend air door motor.
When the ignition switch is in the START or RUN
position, it connects circuit A1 to circuit A21. Circuit
A21 powers circuit F99 through fuse 18 in the PDC.
Circuit F99 powers the coil side of the A/C compres-
sor clutch relay.
Circuit A900 from fuse 3 in the PDC powers circuit
F250 through fuse 21 in the PDC. Circuit F250 pow-
ers the contact side of the A/C compressor clutch
relay.
Circuit E2 from the headlamp dimmer switch pow-
ers the case grounded illumination lamp in the A/C-
heater control switch.
BLOWER MOTOR—MANUAL A/C-HEATER
The blower motor switch has four positions; LOW,
MEDIUM 1, MEDIUM 2, AND HIGH. Circuit A19
8W - 42 AIR CONDITIONING/HEATER
8W-42 AIR CONDITIONING/HEATER
page
INDEX
BLEND DOOR MOTOR—AUTOMATIC
TEMPERATURE CONTROL . . . . . . . . . . . . . . 16
BLOWER MOTOR—AUTOMATIC
TEMPERATURE CONTROL . . . . . . . . . . . . . . 16
BLOWER MOTOR—MANUAL A/C-HEATER . . . . 14
IN-CAR TEMPERATURE SENSOR . . . . . . . . . . 15
MANUAL A/C-HEATER . . . . . . . . . . . . . . . . . . . 14
MODE DOOR MOTOR—AUTOMATIC
TEMPERATURE CONTROL . . . . . . . . . . . . . . 16
RECIRCULATION DOOR MOTOR—AUTOMATIC
TEMPERATURE CONTROL . . . . . . . . . . . . . . 16
SOLAR SENSOR . . . . . . . . . . . . . . . . . . . . . . . . 15
from fuse 7 in the PDC supplies power to the blower
motor. Ground for the blower motor is supplied on
circuit C7 through the blower motor resistor block to
the blower motor switch, through an internal relay in
the A/C-Heater Control head. When the internal
relay energizes, it connects the blower motor switch
to circuit C1. Circuit C1 connects to ground circuit
Z4.
In the HIGH position, the blower motor switch con-
nects circuit C7 from the blower motor directly to
ground on circuits C1 and Z4. In the LOW or
MEDIUM positions, the ground path passes through
the blower motor resistor block to the switch. The
switch connects the circuit C1.
The blower motor resistor block consists of three
resistors connected in series. Depending on blower
motor switch position, the ground path on circuit C7
from the blower motor passes through one or more
resistors to circuit C1.
When the blower motor switch is in the LOW posi-
tion, the ground path passes through all three resis-
tors in the blower motor resistor block to circuit C4.
The blower motor switch connects circuit C4 to cir-
cuits C1 and Z4.
In the MEDIUM 1 position, the ground path
passes through two resistors in the resistor block to
circuit C5. The blower motor switch connects circuit
C5 to circuits C1 and Z4.
In the MEDIUM 2 position, the ground path
passes through one resistor in the resistor block to
circuit C6. The blower motor switch connects circuit
C6 to circuits C1 and Z4.
A/C OPERATION—MANUAL A/C
When the A/C-heater control switch is moved to an
A/C position or the defrost position, the Body Control
ZG
page