Jeep 1997 Grand Cherokee Service Manual page 956

8W - 63 - 18
DESCRIPTION AND OPERATION (Continued)
When the ignition switch is in the RUN position, it
connects circuit A1 from fuse 8 in the PDC to circuit
A22. Circuit A22 powers circuit F71 through fuse 12
in the junction block. Circuit F71 splices to supply
power to the driver and passenger heated seat
switches and provides an input to the heated seat
control modules. Circuit Z1 provides ground for the
control modules and both heated seat switches.
Both heated seat switches have three positions;
OFF, LOW or HIGH. Circuit P7 sends the drivers's
heated seat switch signal to the drivers heated seat
control module. Circuit P8 sends the passenger
heated seat switch signal to the passenger heated
seat control module. In the LOW and HIGH posi-
tions, the drivers heated seat switch connects battery
voltage on circuit F71 to circuit P7 (driver's) or P8
(passenger). The LOW and HIGH position detentes
have a resistor in series between the detente and cir-
cuit P7 or P8. Internal to the switch, voltage from
8W - 63 POWER SEAT
circuit F71 passes through the resistor to circuit P7
or P8. The voltage level on circuit P7 or P8 from the
switch depends on switch position (LOW or HIGH).
After receiving a signal from its heated seat
switch, the heated seat control modules powers the
heater grids in the seat. From either control module,
circuit P87 powers the grid in the drivers seat cush-
ion Current flows out of the seat cushion on circuit
P88 to the grid on the seat back. Circuit Z1 from the
grid in the seat back supplies ground.
Each heated seat control module monitors seat
temperature through a thermistor in each seat.
When seat temperature reaches the temperature
selected by the operator through the heated seat
switch, the control module stops supplying voltage to
the heated seat grids. To maintain selected seat tem-
perature, the control module cycles the grid ON and
OFF.
ZG