Jeep Wrangler TJ. Manual — part 589
the refrigerant system pressure exceeds 3100 - 3375
kPa (450 - 490 psi).
The fitting for the A/C high pressure switch on the
A/C discharge line is equipped with an O-ring seal
and contains a Schrader-type valve, which allows the
switch to be serviced without discharging the refrig-
erant system.
OPERATION
The A/C high pressure switch is electrically con-
nected in series with the A/C low pressure switch
between ground and the powertrain control module
(PCM). The contacts in the A/C high pressure switch
open and close causing the PCM to turn the A/C com-
pressor clutch on and off. This prevents A/C compres-
sor operation when the discharge line pressure
approaches high levels, and also reduces electrical
surging from A/C clutch engagement.
The A/C high pressure switch contacts open when
the A/C discharge line pressure rises above 3100 to
3375 kPa (450 to 490 psi). The A/C high pressure
switch contacts close when the A/C discharge line
pressure drops to 1860 to 2275 kPa (270 to 330 psi).
The A/C high pressure switch is factory-calibrated
and cannot be adjusted or repaired and, if faulty or
damaged, it must be replaced.
DIAGNOSIS AND TESTING
A/C HIGH PRESSURE SWITCH
Before performing diagnosis of the A/C high pres-
sure switch, verify that the refrigerant system has
the correct refrigerant charge (Refer to 24 - HEAT-
ING & AIR CONDITIONING/PLUMBING - STAN-
DARD PROCEDURE - REFRIGERANT SYSTEM
CHARGE)
For circuit descriptions and diagrams, refer to the
appropriate wiring information. The wiring informa-
tion includes wiring diagrams, proper wire and con-
nector repair procedures, further details on wire
harness routing and retention, as well as pin-out and
location views for the various wire harness connec-
tors, splices and grounds.
(1) Disconnect and isolate the negative battery
cable.
(2) Disconnect the wire harness connector from the
A/C high pressure switch.
(3) Check for continuity between both terminals of
the A/C high pressure switch. There should be conti-
nuity. If there is not continuity, replace the faulty
A/C high pressure switch. If there is continuity, test
the A/C high pressure switch sense circuit (Refer to 8
- ELECTRICAL/WIRING DIAGRAM INFORMATION
- DIAGNOSIS AND TESTING). Repair as required.
REMOVAL
NOTE: It is not necessary to discharge the refriger-
ant system to replace the A/C high pressure switch.
(1) Disconnect and isolate the negative battery
cable.
(2) Disconnect the wire harness connector from the
A/C high pressure switch (Fig. 18).
(3) Remove the A/C high pressure switch from the
A/C discharge line and remove and discard the
O-ring seal.
INSTALLATION
NOTE: Use only the specified O-ring as it is made
of special material for R-134a. Use only refrigerant
oil of the type required for the A/C compressor.
(1) Lubricate a new rubber O-ring seal with clean
refrigerant oil and install it on the A/C high pressure
switch fitting.
(2) Install the A/C high pressure switch onto the
A/C
discharge
line.
Hand-tightened
the
switch
securely.
(3) Connect the wire harness connector to the A/C
high pressure switch.
(4) Reconnect the negative battery cable.
Fig. 18 A/C High Pressure Switch - Typical
1 - A/C SUCTION LINE
2 - SERVICE PORT
3 - A/C HIGH PRESSURE SWITCH
4 - A/C COMPRESSOR
5 - MOUNTING BRACKET
6 - A/C DISCHARGE LINE
24 - 22
CONTROLS
TJ
A/C HIGH PRESSURE SWITCH (Continued)
A/C LOW PRESSURE SWITCH
DESCRIPTION
The A/C low pressure switch is a single pole, single
throw, pressure actuated switch that is used to con-
trol evaporator freeze up.
The A/C low pressure switch is mounted on a fit-
ting located on the top of the A/C accumulator. The
A/C low pressure switch fitting on the accumulator is
equipped with an O-ring and contains a Schrader-
type valve, which allows the switch to be serviced
without discharging the refrigerant system.
OPERATION
The A/C low pressure switch monitors the pressure
of the refrigerant leaving the accumulator to the A/C
compressor. When equipped with the 4.0L engine, the
A/C low pressure switch is electrically connected in
series with the A/C high pressure switch, between
ground and the powertrain control module (PCM).
The contacts in the A/C low pressure switch open
or close the path to ground, signaling the PCM to
turn the A/C compressor clutch on and off. This reg-
ulates the refrigerant system pressure and controls
A/C evaporator temperature. Controlling the evapo-
rator temperature prevents condensate water on the
evaporator fins from freezing and obstructing A/C
system air flow.
The A/C low pressure switch contacts are open
when the A/C suction line pressure is approximately
172 kPa (25 psi) or lower. The A/C low pressure
switch contacts will close when the A/C suction line
pressure rises to approximately 276 kPa (40 psi) or
above. Lower ambient temperatures, below approxi-
mately -1° C (30° F), will also cause the A/C low pres-
sure switch contacts to open. This is due to the
pressure/temperature relationship of the refrigerant
in the system.
The A/C low pressure switch is factory-calibrated
and cannot be adjusted or repaired. If the A/C low
pressure switch is faulty or damaged, it must be
replaced.
DIAGNOSIS AND TESTING
A/C LOW PRESSURE SWITCH
NOTE: Lower ambient temperatures, below about
-1° C (30° F), during cold weather will open the A/C
low pressure switch contacts and prevent A/C com-
pressor operation due to the pressure/temperature
relationship of the refrigerant.
Before performing diagnosis of the A/C low pres-
sure switch, verify that the refrigerant system has
the correct refrigerant charge (Refer to 24 - HEAT-
ING & AIR CONDITIONING/PLUMBING - STAN-
DARD PROCEDURE - REFRIGERANT SYSTEM
CHARGE) and that the A/C low pressure switch is
properly installed on the accumulator fitting. If the
A/C low pressure switch is not properly installed, it
may not open the Schrader-type valve in the accumu-
lator fitting, which will prevent the switch from cor-
rectly monitoring the refrigerant system pressure.
For circuit descriptions and diagrams, refer to the
appropriate wiring information. The wiring informa-
tion includes wiring diagrams, proper wire and con-
nector repair procedures, further details on wire
harness routing and retention, as well as pin-out and
location views for the various wire harness connec-
tors, splices and grounds.
(1) With gear selector in Park or Neutral and with
park brake set, start the engine and allow it to idle.
(2) Place the A/C-heater mode control in any A/C
position.
(3) Disconnect the wire harness connector from the
A/C low pressure switch.
(4) Using a suitable jumper wire, install the
jumper wire between the two terminals of the wire
harness connector for the A/C low pressure switch.
The A/C compressor clutch should engage. If the A/C
clutch does engage, replace the faulty A/C low pres-
sure switch. If the A/C clutch does not engage, the
A/C clutch, A/C clutch relay, A/C-heater control , A/C
high pressure switch (4.0L engine application), A/C
pressure transducer (2.4L engine application), PCM,
fuses or related wiring circuits may be defective
(Refer to 8 - ELECTRICAL/WIRING DIAGRAM
INFORMATION - DIAGNOSIS AND TESTING).
Repair as required.
TJ
CONTROLS
24 - 23
REMOVAL
NOTE: Note: It is not necessary to discharge the
refrigerant system to replace the A/C low pressure
switch.
(1) Disconnect and isolate the negative battery
cable.
(2) Disconnect the wire harness connector from the
A/C low pressure switch (Fig. 19).
(3) Remove the A/C low pressure switch from the
fitting on the top of the accumulator and remove and
discard the O-ring seal.
INSTALLATION
NOTE: Use only the specified O-ring as it is made
of special material for R-134a. Use only refrigerant
oil of the type required for the A/C compressor.
(1) Lubricate a new rubber O-ring seal with clean
refrigerant oil and install it on the A/C low pressure
switch fitting.
(2) Install the A/C low pressure switch on the
accumulator. Hand-tightened the switch securely.
(3) Connect the wire harness connector to the A/C
low pressure switch.
(4) Reconnect the negative battery cable.
A/C PRESSURE TRANSDUCER
DESCRIPTION
The A/C pressure transducer (Fig. 20) is a switch
that is installed on a fitting located on the A/C dis-
charge line when equipped with the 2.4L gasoline
engine. An internally threaded fitting on the A/C
pressure transducer connect it to the externally
threaded Schrader-type fitting on the A/C discharge
line. A rubber O-ring seals the connection between
the A/C pressure transducer and the discharge line
fitting. The A/C pressure transducer is connected to
the vehicle electrical system by a molded plastic con-
nector with three terminals.
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 A/C dis-
charge line. The A/C pressure transducer will change
its internal resistance in response to the pressures it
monitors. A Schrader-type valve in the discharge line
fitting permits the A/C pressure transducer to be
removed or installed without disturbing the refriger-
ant in the A/C system.
The powertrain control module (PCM) provides a
five volt reference signal and a sensor ground to the
A/C pressure transducer, then monitors the output
voltage of the A/C pressure transducer on a sensor
return circuit to determine refrigerant pressure. The
PCM is programmed to respond to the A/C pressure
transducer and other sensor inputs by controlling the
operation of the A/C compressor clutch and the radi-
ator cooling fan to help optimize A/C system perfor-
Fig. 19 A/C Low Pressure Switch - Typical
1 - WIRE HARNESS CONNECTOR
2 - ACCUMULATOR
3 - A/C LOW PRESSURE SWITCH
Fig. 20 A/C Pressure Transducer
1 - A/C PRESSURE TRANSDUCER
24 - 24
CONTROLS
TJ
A/C LOW PRESSURE SWITCH (Continued)
mance and to protect the system components from
damage PCM will disengage the A/C compressor
clutch when high side pressure rises above 2971 kPa
(431 psi) or fall below 206 kPa (30 psi). The A/C pres-
sure transducer input to the PCM will also prevent
the A/C compressor clutch from engaging when ambi-
ent temperatures are below about 1.0° C (50° F) due
to
the
pressure/temperature
relationship
of
the
refrigerant.
The A/C pressure transducer is diagnosed using a
DRBIII
t scan tool. Refer to the appropriate diagnos-
tic information.
The A/C pressure transducer cannot be adjusted or
repaired and, if faulty or damaged, it must be
replaced.
DIAGNOSIS AND TESTING
A/C PRESSURE TRANSDUCER
The A/C pressure transducer is tested using a
DRBIII
t 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 A/C 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 A/C
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
Voltage
Possible Indication
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.
REMOVAL
NOTE: Note: It is not necessary to discharge the
refrigerant system to replace the A/C pressure
transducer.
(1) Disconnect and isolate the negative battery
cable.
(2) Disconnect the wire harness connector from the
A/C pressure transducer (Fig. 21).
(3) Remove the A/C pressure transducer from the
A/C discharge line and remove and discard the
O-ring seal.
INSTALLATION
NOTE: Use only the specified O-ring as it is made
of special material for R-134a. Use only refrigerant
oil of the type required for the A/C compressor.
(1) Lubricate a new rubber O-ring seal with clean
refrigerant oil and install it on the A/C pressure
transducer fitting.
(2) Install the A/C pressure transducer onto the
A/C discharge line. Hand-tighten the transducer
securely.
Fig. 21 A/C Pressure Transducer - 2.4L Engine
1 - NUT
2 - A/C DISCHARGE LINE
3 - WIRE HARNESS CONNECTOR
4 - A/C PRESSURE TRANSDUCER
5 - NUT
6 - ACCUMULATOR
7 - A/C SUCTION LINE (FRONT SECTION)
8 - NUT (4)
9 - A/C SUCTION LINE (REAR SECTION)
10 - SECONDARY RETAINING CLIP
11 - A/C CONDENSER
12 - A/C COMPRESSOR
TJ
CONTROLS
24 - 25
A/C PRESSURE TRANSDUCER (Continued)
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