The A/C pressure transducer monitors the pressures
in the high side of the refrigerant system
through its connection to a fitting on the discharge
line. The transducer will change its internal resistance
in response to the pressures it monitors. The
Powertrain Control Module (PCM) or the Engine
Control Module (ECM) depending on engine application,
provides a five volt reference 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/
ECM 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 components from
damage. The A/C pressure transducer input to the
PCM/ECM will also prevent the air conditioning compressor
clutch from engaging when ambient temperatures
are below about 10° C (50° F) due to the
pressure/temperature relationship of the refrigerant.
The Schrader-type valve in the discharge 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 DRBIIIt scan tool. Refer to the appropriate
diagnostic information.
DIAGNOSIS AND TESTING
A/C PRESSURE TRANSDUCER
The A/C pressure transducer is tested using a
DRBIIIt scan tool. Refer to the appropriate diagnostic
information. Before testing the A/C pressure
transducer, be certain that the transducer wire harness
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) or Engine Control Module (ECM) depending
on engine application. The PCM/ECM is programmed
to respond to a low or high refrigerant system pressure
by suppressing operation of the compressor.
Refer to the A/C Pressure Transducer Voltage chart
for the possible conditions indicated by the transducer
voltage reading.
A/C PRESSURE TRANSDUCER VOLTAGE
CHART
Voltage Possible Indication
0.0 1. No sensor supply voltage from
PCM/ECM.
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.
Fig. 19 A/C-Heater Control - Typical, Rear View
1 - MOUNTING TAB (4)
2 - SCREW (4)
3 - A/C-HEATER CONTROL ELECTRICAL CONNECTOR
4 - HEATED SIDEVIEW MIRROR ELECTRICAL CONNECTOR
5 - A/C-HEATER CONTROL
