CABIN HEATER, EXPORT WITH DIESEL ENGINE
•
A Cabin Heater is used in conjunction with the
ATC system. The Cabin Heater is designed to
supply the vehicle's occupants with heat prior to
the engine reaching operating temperature. For
additional information on this system, refer to
Cabin Heater under General Information and
Diagnostic Procedures in this manual.
3.9.1.2 SYSTEM CONTROLS
The ATC Module:
•
is fully addressable with the DRBIII .
•
communicates over the Programmable Commu-
nication Interface Multiplex System (PCI) Bus.
•
provides an A/C request over the PCI Bus to the
Powertrain Control Module (PCM) when com-
pressor operation is desired.
•
for exports with diesel engines, provides a Cabin
Heater activation request over the PCI Bus to the
Front Control Module (FCM) when conditions are
favorable for Cabin Heater operation.
•
uses input from the evaporator temperature sen-
sor to prevent evaporator freeze up while main-
taining optimum cooling performance.
•
uses input from infrared (I/R) sensors, which
measure surface temperature, to maintain occu-
pant comfort levels.
The I/R sensors are mounted in the instru-
ment panel center bezel.
•
can be operated in a manual mode.
•
provides a blower relay on request over the PCI
Bus to the Front Control Module (FCM) when
blower operation is desired.
•
controls front blower operating speed, providing
10 speeds in manual mode and infinite speeds in
automatic mode.
•
controls rear blower operating speed, providing
10 speeds in manual mode and infinite speeds in
automatic mode.
The separate front and rear Blower Motor
Controllers operate as follows: When blower
operation is desired, the Blower Motor Con-
troller provides a 10.0 volt signal to the ATC
Module over a control circuit. The ATC Mod-
ule provides a variable duty cycle ground to
the 10.0 volt signal based on input from the
blower switch. When the blower switch is set
to LO speed, the ATC Module provides a short
duty cycle (less time grounding the signal
voltage). As higher blower speeds are re-
quested, the ATC Module increases the duty
cycle (more time grounding the signal volt-
age). When the blower switch reaches HI
GENERAL INFORMATION
speed, the duty cycle increases to where the
signal pattern is almost a flat line (with brief
voltage spikes).
•
controls the front and rear electronic door actua-
tors' operation.
A simplified control system for operation of
the mode, recirculation, and temperature con-
trol actuators provides positive positioning
without the complexity of feedback from posi-
tion sensors. The ATC Module knows the
number of operating actuator revolutions re-
quired for full door travel as well as the
number of actuator commutator pulses per
revolution. Using these parameters, the ATC
Module runs the actuator for the number of
commutator pulses that correspond to the
desired door position. To maintain accuracy,
the system recalibrates itself periodically at
known zero and full travel conditions.
•
activates and deactivates the Rear ATC Switch.
The Rear ATC Switch (Three-Zone Only):
•
provides desired rear blower speed input to the
ATC Module.
•
provides desired rear blend and mode door posi-
tion input to the ATC Module.
The Dual-Zone ATC system uses:
•
two front, two-wire electronic blend door actua-
tors.
•
one front, two-wire electronic mode door actuator.
•
one, two-wire electronic recirculation door actua-
tor.
The Three-Zone ATC system uses:
•
two front, two-wire electronic blend door actua-
tors.
•
one front, two-wire electronic mode door actuator.
•
one, two-wire electronic recirculation door actua-
tor.
•
one rear, two-wire electronic blend door actuator.
•
one rear, two-wire electronic mode door actuator.
System Relays
•
The Integrated Power Module (IPM) houses and
provides power to the A/C Clutch Relay, Front
Blower Motor Relay, and Rear Blower Motor
Relay.
3.9.1.3 SYSTEM REVISIONS
Revisions to the 2003 ATC system include:
•
all new version 13 (Two-Zone) and 0F (Three-
Zone) system software.
17