Grand Cherokee 2WD L6-4.0L VIN S (1997)
Blower Motor Power Module: Description and Operation
Automatic Temperature Control (ATC) Module
CIRCUIT OPERATION
Circuit F71 supplies battery voltage to the Automatic Temperature Control (ATC) module when the ignition switch is in the RUN position. Circuit
F60 from fuse 20 in the junction block connects to the ATC module. Circuit F60 is HOT at all times. Circuit Z4 provides ground for the ATC
module.
Circuit E2 from the headlamp dimmer switch connects to the ATC module.
The ATC module communicates with other vehicle modules and controllers on the CCD bus. Circuits D1 and D2 for the CCD Bus connect to the
ATC module.
When the A/C select switch in the Automatic Temperature Control (ATC) control head closes circuit C90 provides the A/C select signal to the
Body Control Module (BCM). After receiving the input, the BCM signals the Powertrain Control Module (PCM) on the CCD bus.
The A/C low pressure and high pressure switches are wired in series and connect to ground on circuit Z1. Circuit C3 from the PCM connects to the
low pressure switch. Circuit C21 connects the low pressure switch to the high pressure switch. The high pressure switch connects circuit C21 to
ground circuit Z1. If the A/C low pressure and high pressure switches are closed, the PCM senses the A/C request signal on circuit C3.
After sensing the A/C request signal, the PCM supplies ground for the coil side of A/C compressor clutch relay on circuit C13. Circuit F99 from
fuse 18 in the PDC powers the coil side of the relay
When the PCM grounds the A/C compressor clutch relay, the contacts close and connects circuit F25O from fuse 21 in the PDC to circuit C2.
Circuit C2 supplies power to the case grounded A/C compressor clutch.
The A/C compressor clutch has a built-in diode. The diode controls the induced voltage that results from the magnetic field collapsing when the
clutch disengages. The diode provides a current path to protect other components and systems.
