Chrysler Dodge Caravan 2002 Manual page 2253

24 - 10 CONTROLS - FRONT
A/C PRESSURE TRANSDUCER
DESCRIPTION - A/C PRESSURE TRANSDUCER
Fig. 2 A/C Pressure Transducer
1 - RIGHT FRONT STRUT TOWER
2 - CONNECTOR
3 - A/C PRESSURE TRANSDUCER
4 - RIGHT WIPER MODULE DRAIN TUBE
5 - HIGH SIDE SERVICE PORT
6 - LIQUID LINE
The A/C pressure transducer (Fig. 2) is a switch
that is installed on a fitting located on the refriger-
ant liquid line between the filter-drier and the
expansion valve in the right rear corner of the engine
compartment. An internally threaded hex fitting on
the transducer connects it to the externally threaded
Schrader-type fitting on the liquid line. A rubber
O-ring seals the connection between the transducer
and the liquid line fitting. Three terminals within a
molded plastic connector receptacle on the top of the
transducer connect it to the vehicle electrical system
through a take out and connector of the headlamp
and dash wire harness.
The A/C pressure transducer cannot be adjusted or
repaired and, if faulty or damaged, it musty be
replaced.
OPERATION
The A/C pressure transducer monitors the pres-
sures in the high side of the refrigerant system
through its connection to a fitting on the liquid line.
The transducer will change its internal resistance in
response to the pressures it monitors. The Power-
train Control Module (PCM) provides a five volt ref-
erence signal and a sensor ground to the transducer,
then monitors the output voltage of the transducer
on a sensor return circuit to determine refrigerant
pressure. The PCM is programmed to respond to this
and other sensor inputs by controlling the operation
of the air conditioning compressor clutch and the
radiator cooling fan to help optimize air conditioning
system performance and to protect the system com-
ponents from damage. The A/C pressure transducer
input to the PCM will also prevent the air condition-
ing compressor clutch from engaging when ambient
temperatures are below about 10° C (50° F) due to
the pressure/temperature relationship of the refriger-
ant. The Schrader-type valve in the liquid line fitting
permits the A/C pressure transducer to be removed
or installed without disturbing the refrigerant in the
system. The A/C pressure transducer is diagnosed
using a DRBIII scan tool. Refer to the appropriate
diagnostic information.
DIAGNOSIS AND TESTING - A/C PRESSURE
TRANSDUCER
The A/C pressure transducer is tested using a
DRBIII scan tool. Refer to the appropriate diagnos-
tic information. Before testing the A/C pressure
transducer, be certain that the transducer wire har-
ness connection is clean of corrosion and properly
connected. For the air conditioning system to operate,
an A/C pressure transducer voltage reading between
0.451 and 4.519 volts is required. Voltages outside
this range indicate a low or high refrigerant system
pressure condition to the Powertrain Control Module
(PCM). The PCM is programmed to respond to a low
or high refrigerant system pressure by suppressing
operation of the compressor. Refer to the A/C Pres-
sure Transducer Voltage table for the possible condi-
tion indicated by the transducer voltage readings.
A/C PRESSURE TRANSDUCER VOLTAGE
VOLTAGE
0.0 1. NO SENSOR SUPPLY
VOLTAGE FROM PCM.
2. SHORTED SENSOR CIRCUIT.
3. FAULTY TRANSDUCER.
0.150 TO 0.450 1. AMBIENT TEMPERATURE
BELOW 10° C (50° F).
2. LOW REFRIGERANT
SYSTEM PRESSURE.
0.451 TO 4.519 1. NORMAL REFRIGERANT
SYSTEM PRESSURE.
4.520 TO 4.850 1. HIGH REFRIGERANT
SYSTEM PRESSURE.
5.0 1. OPEN SENSOR CIRCUIT.
2. FAULTY TRANSDUCER.
POSSIBLE INDICATION
RS