Dodge Neon / Neon SRT-4. Manual — part 428
A/C LOW PRESSURE SWITCH
DESCRIPTION
The A/C low pressure switch is a single pole, single
throw, pressure actuated switch that is installed in a
threaded port into the suction passage of the accu-
mulator on 2.0L LHD models or in a threaded port
into the suction passage of the expansion valve on
2.4L and RHD models. The accumulator fitting on
2.0L LHD models contain a Schrader type valve,
which allows the switch to be serviced without dis-
charging the refrigerant system and is equipped with
a O-ring to seal the switch plumbing connection. The
A/C low pressure switch on 2.4l and RHD models can
only be serviced with the refrigerant system dis-
charged.
The A/C low pressure switch is factory calibrated
and cannot be adjusted or repaired and, if faulty or
damaged, it must be replaced.
OPERATION
The A/C low pressure switch is electrically con-
nected in series with the A/C-heater control mode
switch and the A/C high pressure switch, between
ground and the powertrain control module (PCM).
The A/C low pressure switch contact opens or closes
the path the ground, signaling the PCM to turn the
A/C compressor clutch on and off. This regulates the
refrigerant system pressure and controls evaporator
coil temperature. Controlling the evaporator temper-
ature prevents condensate water on the evaporator
fins from freezing and obstructing air conditioning
system air flow.
On 2.0L LHD models, the A/C low pressure switch
contacts are open when the suction pressure is
approximately 152 kPa (22 psi) or lower. The switch
contacts will close when the suction pressure rises to
approximately 234 to 262 kPa (34 to 38 psi) or above.
Lower ambient temperatures, below approximately
-1° C (30° F), will also cause the A/C low pressure
switch contacts to open. This is due to the pressure/
temperature relationship of the refrigerant in the
system.
On 2.4L and RHD models, the A/C low pressure
switch contacts are open when the suction pressure
is approximately 96 kPa (14 psi) or lower. The switch
contacts will close when the suction pressure rises to
approximately 234 to 262 kPa (34 to 38 psi) or above.
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, PCM or ECM (depending on
engine application), fuses or related wiring circuits
may be defective (Refer to 8 - ELECTRICAL/WIRING
DIAGRAM
INFORMATION
-
DIAGNOSIS AND
TESTING). Repair as required.
REMOVAL
2.0L LHD MODELS
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. 14).
(3) Remove the A/C low pressure switch from the
fitting on the top of the accumulator.
(4) Remove the O-ring seal from the accumulator
and discard.
24 - 20
CONTROLS
PL/SRT-4
2.4L AND RHD MODELS
WARNING: THE REFRIGERATION SYSTEM MUST
BE
COMPLETELY
RECOVERED
BEFORE
PRO-
CEEDING WITH THIS OPERATION.
(1) Recover the refrigerant from the refrigerant
system (Refer to 24 - HEATING & AIR CONDITION-
ING/PLUMBING
-
STANDARD
PROCEDURE
-
REFRIGEANT SYSTEM RECOVERY).
(2) Disconnect and isolate the negative battery
cable.
(3) Disconnect the wire harness connector from the
A/C low pressure switch (Fig. 15).
(4) Using a sender unit removal socket or equiva-
lent, remove the A/C low pressure switch from the
expansion valve.
(5) Remove the O-ring seal from the pressure
switch fitting and discard.
(6) Install plug in, or tape over the opened expan-
sion valve port.
INSTALLATION
2.0L LHD MODELS
NOTE: Replace the O-ring seal before installing the
A/C low pressure switch.
(1) Lubricate a new O-ring seal with clean refrig-
erant oil and install it on the accumulator fitting.
Use only the specified O-rings as they are made of a
special material for the R-134a system. Use only
refrigerant oil of the type recommended for the A/C
compressor in the vehicle.
(2) Install and tighten the A/C low pressure switch
onto the accumulator fitting. The switch should be
hand-tightened securely onto the accumulator fitting.
(3) Connect the wiring harness connector to the
A/C low pressure switch.
(4) Reconnect the negative battery cable.
2.4L AND RHD MODELS
(1) Remove the tape or plug from the opened
expansion valve port.
(2) Lubricate a new rubber O-ring seal with clean
refrigerant oil and install it on the A/C low pressure
switch fitting. Use only the specified O-ring as it is
made of a special material for the R-134a system.
Use only refrigerant oil of the type recommended for
the A/C compressor in the vehicle.
(3) Using a sender unit socket or equivalent,
install the A/C low pressure switch onto the expan-
sion valve. Tighten the switch securely.
(4) Connect the wire harness connector to the A/C
low pressure switch.
(5) Reconnect the negative battery cable.
(6) Evacuate the refrigerant system (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - REFRIGERANT SYS-
TEM EVACUATE).
Fig. 14 A/C Low Pressure Switch - Typical
1 - ACCUMULATOR
2 - A/C LOW PRESSURE SWITCH
3 - WIRE HARNESS CONNECTOR
Fig. 15 A/C Low Pressure Switch
1 - A/C EXPANSION VALVE
2 - A/C LOW PRESSURE SWITCH
3 - LIQUID LINE
4 - SUCTION LINE
PL/SRT-4
CONTROLS
24 - 21
A/C LOW PRESSURE SWITCH (Continued)
(7) Recharge the refrigerant system (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - REFRIGERANT SYS-
TEM CHARGE).
BLOWER MOTOR RESISTOR
BLOCK
DESCRIPTION
The blower motor resistor (Fig. 16) is located in the
cowl, at the base of the windshield. There are two
different
blower
motor
resistors
depending
on
whether the vehicle is equipped with A/C or not.
The blower motor resistor is mounted to the dash
panel within the engine compartment. The resistor
consists of a molded plastic mounting plate with an
integral wire connector receptacle. Concealed behind
the mounting plate are coiled resistor wires con-
tained within a protective stamped steel cage. The
blower motor resistor is accessed for service by
removing the cowl top screen.
OPERATION
The blower motor resistor is connected to the vehi-
cle electrical system through a dedicated take out
and connector of the vehicle harness. The blower
motor resistor has multiple resistor wires, each of
which will reduce the current flow through the
blower motor to change the blower motor speed. The
blower motor switch directs the ground path for the
blower motor through the correct resistor wire to
obtain the selected speed.
With the blower motor switch in the lowest speed
position, the ground path for the motor is applied
through all of the resistor wires. Each higher speed
selected with the blower motor switch applies the
blower motor ground path through fewer of the resis-
tor wires, increasing the blower motor speed. When
the switch is in the highest speed position, blower
motor resistor is bypassed and the blower motor
receives a direct path to ground.
The blower motor resistor cannot be adjusted or
repaired and, if faulty or damaged, it must be
replaced.
DIAGNOSIS AND TESTING
BLOWER MOTOR RESISTOR
WARNING: On vehicles equipped with airbags, dis-
able the airbag system before attempting any steer-
ing wheel, steering column, or instrument panel
component diagnosis or service. Disconnect and
isolate the negative battery (ground) cable, then
wait two minutes for the airbag system capacitor to
discharge before performing further diagnosis or
service. This is the only sure way to disable the air-
bag system. Failure to take the proper precautions
could result in accidental airbag deployment and
possible personal injury or death.
NOTE: For circuit descriptions and diagrams, refer
to the appropriate wiring information. The wiring
information includes wiring diagrams, proper wire
and connector repair procedures, further details on
wire harness routing and retention, as well as pin-
out and location views for the various wire harness
connectors, splices and grounds.
(1) Disconnect and isolate the negative battery
cable.
(2) Disconnect the wire harness connector from the
blower motor resistor (Refer to 24 - HEATING & AIR
CONDITIONING/CONTROLS/BLOWER
MOTOR
RESISTOR - REMOVAL).
(3) Using
an
ohmmeter,
check
for
continuity
between all of the blower motor resistor terminals. In
each case there should be continuity. If OK, repair
the wire harness circuits between the blower motor
switch and the blower motor resistor or blower motor
as required. If not OK, replace the faulty blower
motor resistor.
Fig. 16 Blower Motor Resistor
1 - BLOWER MOTOR RESISTOR
2 - RESISTORS
24 - 22
CONTROLS
PL/SRT-4
A/C LOW PRESSURE SWITCH (Continued)
REMOVAL
WARNING: The blower motor resistor may get very
hot during normal operation. If the blower motor
was turned on prior to servicing the blower motor
resistor, wait five minutes to allow the blower motor
resistors to cool before performing diagnosis or
service. Failure to take this precaution can result in
possible personal injury.
CAUTION: Do not operate the blower motor with the
blower motor resistor removed from the circuit.
Failure to take this precaution can result in vehicle
damage.
(1) Disconnect and isolate the negative battery
cable.
(2) Remove the windshield wipers (Refer to 8 -
ELECTRICAL/WIPERS/WASHERS/WIPER ARMS -
REMOVAL).
(3) Remove the cowl top screen (Refer to 23 -
BODY/EXTERIOR/COWL
GRILLE
SCREEN
-
REMOVAL).
(4) Disconnect the wire harness connector from the
blower motor resistor (Fig. 17).
(5) Disengage the retaining clip and remove the
blower motor resistor from the engine compartment.
INSTALLATION
(1) Position the blower motor resistor into the
engine compartment.
(2) Install the blower motor resistor into the cowl
and engage the retaining clip.
(3) Connect the wire harness connector to the
blower motor resistor.
(4) Install the cowl top screen (Refer to 23 -
BODY/EXTERIOR/COWL
GRILLE
SCREEN
-
INSTALLATION).
(5) Install the windshield wipers (Refer to 8 -
ELECTRICAL/WIPERS/WASHERS/WIPER ARMS -
INSTALLATION).
(6) Reconnect the negative battery cable.
EVAPORATOR TEMPERATURE
SENSOR - 2.4L RHD MODELS
DESCRIPTION
2.4L and RHD models equipped with A/C use an
evaporator temperature sensor. The evaporator tem-
perature sensor is a switch with a sensing probe that
is inserted between the evaporator coil fins at the
coldest point on the face of the A/C evaporator. The
evaporator temperature sensor prevents condensate
water on the evaporator coil from freezing and
obstructing A/C system air flow by cycling the com-
pressor clutch OFF when evaporator temperature
drops below the freeze point. It cycles the compressor
back ON when the evaporator temperature rises
above the freeze point. The sensor probe is filled with
a special silicone-based thermal grease. Three termi-
nals within a molded plastic connector receptacle on
the sensor connect it to the vehicle electrical system
through a take out and connector of the HVAC wire
harness. The evaporator temperature sensor can be
replaced without having to remove the HVAC hous-
ing from the vehicle.
The evaporator temperature sensor cannot be
adjusted or repaired and, if faulty or damaged, it
must be replaced.
DIAGNOSIS AND TESTING
EVAPORATOR TEMPERATURE SENSOR
The work area and vehicle must be between 16° C
(60° F) and 32° C (90° F) when testing the evaporator
temperature sensor.
(1) Disconnect the wire harness connector from the
evaporator temperature sensor located behind the
glove box (Fig. 18).
(2) Start engine and set A/C to low blower motor
speed, panel, full cool, and RECIRC.
(3) Using a voltmeter, check for battery voltage
between Pin 1 and 2. If no voltage is detected, there
is no power to the evaporator temperature sensor.
Check wiring and fuses (Refer to 8 - ELECTRICAL/
WIRING DIAGRAM INFORMATION - DIAGNOSIS
AND TESTING).
Fig. 17 Blower Motor Resistor - Typical
1 - BLOWER MOTOR RESISTOR
2 - ELECTRICAL CONNECTOR
PL/SRT-4
CONTROLS
24 - 23
BLOWER MOTOR RESISTOR BLOCK (Continued)
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