Content .. 693 694 695 696 ..

Chrysler Town, Dodge Caravan. Manual - part 695

allow the rear defrost to operate in the RUN posi-
tion. This circuit is electronically controlled and
continuously monitored for malfunctions.

3.8.3

ELECTRICAL INPUTS

Headlamp battery supplies 1 & 2 — 12 volt
input on pins 1 and 2. Battery supply voltage for
switching headlamp circuits only.

Module battery supply — 12 volt input on pin 9.
Battery supply voltage for all other FCM opera-
tions.

Power ground — Ground source on pin 8 for all
FCM operations.

Ignition switch RUN or START position status
— 12 volt input on pin 37. Allows the FCM to
determine the ignition switch status for related
FCM operations.

Ignition switch START only status — 12 volt
input on pin 19. Allows the FCM to discriminate
between RUN/START input and START for related
FCM operations.

PCI Bus — Approximately 7.5 volt input on pin 22.
Allows the FCM to communicate with other mod-
ules on the vehicle bus.

Stop lamp Switch status — 12 volt input on pin
44. Provides for brake shift interlock function.

Horn Switch — Ground input on pin 17. Primary
means for engaging the horn.

Back-up switch — Ground input on pin 39. Input
is converted to a PCI Bus status message for use by
other modules.

Wiper park switch — Ground input on pin 16.
Used to determine park placement of wipers. Also
used as feedback to FCM to determine correct
operating mode of wipers.

Washer fluid level switch — Ground input to
pull-up on pin 18. Ground is switched into the
circuit when washer bottle fluid level is low.

Brake fluid level switch — Ground input to
pull-up on pin 36. Ground is switched into the
circuit when brake fluid level is low.

Ambient temperature sensor — Resistive input
to pull-up on pin 25. Corresponding voltage level is
converted to a PCI Bus message for use by other
modules on the bus.

Right park lamp outage — 12 volt input on pin
21. Used to determine if right park lamp circuit is
operating properly.

Left park lamp outage — 12 volt input on pin 41.
Used to determine if left park lamp circuit is
operating properly.

Battery IOD — 12 volt input on pin 20. The FCM
enters a low power consumption mode when the
ignition is turned OFF. This low current draw
battery supply keeps the microprocessor function-
ing in the low power mode.

Battery (+) connection detection — 12 volt
input on pin 38. The battery connection on the PDC
incorporates the use of an internal switch to deter-
mine if the connector is properly mated and the
Connector Positive Assurance (CPA) is engaged. If
the CPA is not properly engaged, a voltage on pin 38
will be interpreted as an unseated connector and a
fault will set.

Flash programming voltage — 20 volt input on
pin 42. When a DRBIII

t is connected and the

proper flash reprogramming sequence is selected,
the 20 volt signal will be applied through pin 42.

3.9

HEATING & A/C SYSTEM

3.9.1

AUTOMATIC TEMPERATURE
CONTROL (ATC)

CAUTION: Automatic Temperature Control
(ATC) Modules with software versions 41 and
0A used in 2001 and 2002 RS/RG vehicles are
NOT compatible with software versions 13
and 0F used in 2003 RS/RG vehicles. Do NOT
install an ATC Module with software version
41 or 0A in a 2003 RS/RG vehicle or an ATC
Module with software version 13 or 0F in a
2001 or 2002 RS/RG vehicle. Use the DRBIII

to verify which version software the ATC
Module is using by selecting Body Systems,
Automatic Temperature Control, and then
selecting Module Display.

3.9.1.1

SYSTEM AVAILABILITY

EXCEPT EXPORT

•

The ATC system is a Three-Zone Air Conditioning
System.

EXPORT

•

Two different types of systems are currently
available for these vehicles.

Dual-Zone Air Conditioning System for all
vehicles with 2.4L and 2.5L engines and all
SWB vehicles with 3.3L engines.

Three-Zone Air Conditioning System for all
LWB vehicles.

GENERAL INFORMATION

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

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.

GENERAL INFORMATION

to verify which version software the ATC
Module is using by selecting Body Systems,
Automatic Temperature Control, and then
selecting Module Display.

•

a Two-Zone HVAC system on select models.

•

a Cabin Heater used in conjunction with the ATC
system. For additional information on this sys-
tem, refer to The AC Cooldown Test, under 3.9.1.4
System Diagnostics in this General Information
section, and refer to Cabin Heater under General
Information and Diagnostic Procedures in this
manual.

•

deletion of the rear IR sensor.

3.9.1.4

SYSTEM DIAGNOSTICS

Fault detection is through active and stored Diag-
nostic Trouble Codes (DTCs)

•

DTCs are displayed by the DRBIII

•

Active DTCs are those which currently exist in
the system. The condition causing the fault must
be repaired in order to clear this type of DTC.

•

Stored DTCs are those which occurred in the
system since the ATC Module received the last
9clear diagnostic info9 message.

The AC Cooldown Test:

•

is actuated with the DRBIII

•

checks A/C system performance based on evapo-
rator temperature sensor input.

•

forces the ATC to initiate the Cabin Heater Acti-
vation request when the vehicle is equipped with
a Diesel Cabin Heater Assist.

WARNING: DO NOT OPERATE THE DCHA IN
AN ENCLOSED AREA SUCH AS A GARAGE
THAT

DOES

NOT

HAVE

EXHAUST

VENTILATION FACILITIES. ALWAYS VENT
THE DCHA’s EXHAUST WHEN OPERATING
THE

DCHA.

REFER

VENTING

THE

DCHA’s EXHAUST UNDER CABIN HEATER IN
THE GENERAL INFORMATION PORTION OF
THIS

SECTION

FOR

PROPER

EXHAUST

VENTING

INSTRUCTIONS.

FAILURE

FOLLOW

THESE

INSTRUCTIONS

MAY

RESULT IN PERSONAL INJURY OR DEATH.

CAUTION: Do not activate the A/C Cooldown
Test with the engine off. Failure to follow
these instructions may result in internal
damage to the DCHA Heater Module.

The FCM monitors the PCI bus for the Cabin
Heater Activation request. The request car-
ries the status bit that the FCM requires to
activate its’ Cabin Heater Assist Control out-
put. This output is a low side driver (coming
from FCM pin 15) which supplies a ground
signal to the Cabin Heater (pin 5). When the
Cabin Heater receives this ground signal in-
put, it interprets this as an activation signal.

The FCM low side driver is also capable of
diagnostic sensing. The driver will sense an
open circuit when the driver is off, and will
sense a short to voltage when the driver is on.
The FCM will set DTCs for both of these types
of faults. For additional information, refer to
Cabin Heater under General Information and
Diagnostic Procedures in the manual.

•

will not run the air conditioning portion of this
test if ambient temperature is below 12°C (53°F).

The forced Cabin Heater activation will occur
even if the air conditioning portion of this test
fails to initiate because AC Cooldown test
criteria was not met. When activated, the
DCHA will operate for approximately seven
minutes. Three minutes to run and four min-
utes to purge.

•

will pass the air conditioning portion of this test
if the evaporator temperature drops 6.7°C (20°F)
within two minutes of starting this test.

•

messages (air conditioning related only) display
on the DRBIII

t after running this test.

These messages will clear after paging back
out of this test. Therefore, it is important to
note all of the AC Cooldown test messages
before doing so.

All Cabin Heater-related DTCs display under
Cabin Heater, Read DTCs.

•

will cause the DELAY and Snowflake VF seg-
ments on the ATC to flash for 162 seconds (RG
with DCHA only). If the air conditioning portion
of this test fails, the DELAY and Snowflake VF
segments will continue to flash until the vehicle
is driven more than three miles.

GENERAL INFORMATION

3.9.2

MANUAL TEMPERATURE CONTROL
(MTC)

CAUTION:

Manual

Temperature

Control

(MTC) Modules with software versions 0614
and 0700 used in 2001 and 2002 RS/RG
vehicles are NOT compatible with software
version 0802 used in 2003 RS/RG vehicles.
Do NOT install an MTC Module with software
version 0614 or 0700 in a 2003 RS/RG vehicle.
Use the DRBIII

to verify which version

software

the

MTC

Module

using

selecting Body Systems, HVAC, and then
selecting Module Display.

3.9.2.1

SYSTEM AVAILABILITY

EXCEPT EXPORT

•

Three different types of systems are currently
available for these vehicles.

Single-Zone Air Conditioning System

Dual-Zone Air Conditioning System

Three-Zone Air Conditioning System

EXPORT

•

Two different types of systems are currently
available for these vehicles.

Single-Zone Air Conditioning System

Dual-Zone Air Conditioning System

CABIN HEATER, EXPORT WITH DIESEL ENGINE

•

A Cabin Heater is used in conjunction with the
HVAC 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.

3.9.2.2

SYSTEM CONTROLS

The A/C-Heater Control Module:

•

is fully addressable with the DRBIII

•

communicates over the Programmable Commu-
nication Interface Multiplex System (PCI) Bus.

•

provides an A/C request to the Powertrain Con-
trol Module (PCM) over the PCI Bus when com-
pressor operation is desired.

•

uses input from the evaporator temperature sen-
sor to prevent evaporator freeze up while main-
taining optimum cooling performance.

•

for exports with diesel engines, provides a Cabin
Heater activation request to the Front Control

Module (FCM) over the PCI Bus when conditions
are favorable for Cabin Heater operation.

•

provides a blower relay on request to the Front
Control Module (FCM) over the PCI Bus when
blower operation is desired.

•

controls front blower operating speed. The five
speed settings are Low, M1, M2, M3, and High.

•

controls EBL operation.

•

on three-zone systems, activates and deactivates
the Rear A/C-Heater Control.

•

on three-zone systems, controls rear blower oper-
ating speed. The three speed settings are Low,
Med, and High.

•

controls the front and the three-zone system rear
electronic door actuators’ 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 A/C - Heater Control Module
knows the number of operating actuator rev-
olutions required for full door travel as well as
the number of actuator commutator pulses
per revolution. Using these parameters, the
A/C - Heater Control Module runs the actua-
tor 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.

On Three-Zone systems, the Rear A/C-Heater Con-
trol:

•

controls rear blower motor operating speed. The
three blower speeds are Low, Med, and High.

•

provides desired rear blend and mode door posi-
tion input to the A/C-Heater Control Module.

The Single-Zone HVAC system uses:

•

one, two-wire electronic blend door actuator.

•

one, two-wire electronic mode door actuator.

•

one, two-wire electronic recirculation door actua-
tor.

The Dual-Zone HVAC system uses:

•

two, two-wire electronic blend door actuators.

•

one, two-wire electronic mode door actuator.

•

one, two-wire electronic recirculation door actua-
tor.

The Three-Zone HVAC system uses:

•

two front, two-wire electronic blend door actua-
tors.

•

one front, two-wire electronic mode door actuator.

GENERAL INFORMATION

Content .. 693 694 695 696 ..