DODGE RAM 1999 Service Owners Manual

specification .......... A .. Require repair or replacement.
Circuit shorted ......... A .. Require repair or replacement.
Connector melted,
affecting performance .. A ........... (1) Require repair or
replacement.
Connector melted, not
affecting performance .. 2 ........... ( 1) Suggest repair or
replacement.
Connector missing ....... C ............ Require replacement.
Diode open .............. A .. Require repair or replacement.
Diode shorted ........... A .. Require repair or replacement.
Insulation damaged,
conductors exposed ..... A .. Require repair or replacement.
Insulation damaged,
conductors not exposed . 1 ............ Suggest replacement.
Protective shield
(conduit) melted ....... B ........ ( 1) Require replacement.
Protective shield
(conduit) missing ...... C ............ Require replacement.
Routed incorrectly ...... B ................. Require repair.
Secured incorrectly ..... B ................. Require repair.
Terminal broken ......... A .. Require repair or replacement.
Terminal burned, affecting
performance ............ A ........... ( 1) Require repair or
replacement.
Terminal burned, not
affecting performance .. 2 .. Suggest repair or replacement.
Terminal corroded,
affecting performance .. A .. Require repair or replacement.
Terminal corroded, not
affecting performance .. 2 .. Suggest repair or replacement.
Terminal loose, affecting
performance ............ B .. Require repair or replacement.
Terminal loose, not
affecting performance .. 1 .. Suggest repair or replacement.
Voltage drop out of
specification .......... A .. Require repair or replacement.
( 1) - Determine cause and correct prior to repair or
replacement of part.









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A/C -H EA TE R S YSTE M

1999 D odge P ic ku p R 1500
1999 MANUAL A/C-HEATER SYSTEMS
CHRYSLER
Dakota, Durango & Ram Pickup
SPECIFICATIONS
SPECIFICATIONS








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Application Specification
Compressor Type .............................. Sanden SD-7H15 7-Cyl.
Compressor Belt Tension ........................................ ( 1)
Refrigerant (R-134a) Capacity
With Rear A/C Unit ....................................... 30 ozs.
Without Rear A/C Unit .................................... 28 ozs.
System Oil Capacity
Dakota & Ram Pickup ................................. ( 2) 8.1 ozs.
Durango
With Rear A/C Unit ................................. ( 2) 8.0 ozs.
Without Rear A/C Unit .............................. ( 2) 5.5 ozs.
System Operating Pressures ( 3)
High Side ......................... 190-220 psi (13.4-15.5 kg/cm
)
Low Side .............................. 32-40 psi (2.2-2.8 kg/cm)
( 1) - Dynamic tensioner automatically adjusts belt. Tension is okay if
indicator is within marked limits on belt tensioner.
( 2) - Use SP-20 PAG refrigerant oil.
( 3) - Measured at ambient air temperature of 80
F (27C).








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WARNING: To avoid injury from accidental air bag deployment, read and
carefully follow all SERVICE PRECAUTIONS and DISABLING &
ACTIVATING AIR BAG SYSTEM procedures in AIR BAG SYSTEM SAFETY
article.
CAUTION: When battery is disconnected, radio will go into anti-theft
protection mode. Obtain radio anti-theft protection code from
owner prior to servicing vehicle.
DESCRIPTION
These systems are a blend-air type. Outside air enters
through a cowl at base of the windshield and flows through a plenum
chamber into blower housing. Airflow velocity is controlled by blower
speed selector switch. Air flows across evaporator and is directed by
a blend-air door to go either through or by-pass the heater core.
On Dakota and Durango, temperature control cable operates
blend-air door and allows immediate control of outlet air temperature.
It also controls operation of recirculation door. On Ram Pickup,
temperature is regulated by a blend-air servo motor controlled from
A/C-heater control panel rotary temperature dial. On all models, mode
selector switch controls vacuum-operated doors to direct conditioned
air to selected outlets.
Durango may also be equipped with an optional rear A/C unit.
The rear A/C unit consists of a blower motor and evaporator. It will
only operate while the front A/C is on. The optional rear A/C-heater
unit is controlled using fan and temperature switches.

OPERATION
CONTROL PANEL
Blower Motor Switch
Fan speed is controlled with a rotary switch. On front A/C-
heater systems, there are 4 different fan speed settings. Low, medium-
low, medium-high, and high. On rear A/C-heater systems, there are 3
different fan speed settings. Low, medium, and high.
Mode Control Knob
Mode rotary switch is used to change direction of air flow.
There are 7 different modes of operation: recirculation, panel with
A/C, floor/panel, panel without A/C (vent), floor, floor/defrost, and
defrost.
Temperature Control Knob
Temperature rotary switch controls temperature blend/air door
position by a cable on Dakota and Durango, and by vacuum actuator for
Ram Pickup. When cold temperature is selected, no air flows across
heater core. When hot temperature is selected, all air flows through
heater core. Temperature may vary by any setting between cold and hot.
CLUTCH CYCLING PRESSURE SWITCH
Dakota & Ram Pickup
Clutch cycling low pressure switch is mounted on a Schrader-
type valve fitting that is part of the accumulator. It is connected in
series with the high pressure cut-off switch and control panel,
between ground and PCM. Switch contacts open and close due to changes
in A/C system pressure. Opening and closing of switches will cause PCM
to turn compressor clutch on and off, regulating system pressure which
controls temperature of evaporator.
Clutch cycling low pressure switch contacts are normally open
when suction (low side) pressure drops below 25 psi (1.8 kg/cm
) on
Ram Pickup; 20.5 psi (1.4 kg/cm) on Dakota. Extreme cold weather will
also open contacts. When contacts are open, PCM will de-energize
compressor clutch relay, disengaging compressor clutch.
Clutch cycling pressure switch contacts will close when
suction (low side) pressure rises above 43 psi (3.0 kg/cm
) on Ram
Pickup or 36 psi (2.5 kg/cm) on Dakota. When contacts are closed, PCM
will energize compressor clutch relay, engaging compressor clutch.
ELECTRONIC CYCLING CLUTCH SWITCH
Durango
The electronic cycling clutch switch is mounted to Thermal
Expansion Valve (TXV), also referred to as an "H" valve, in engine
compartment. It provides evaporator temperature to the PCM. Using this
information, the PCM will cycle the compressor clutch to prevent
evaporator icing. The switch is used for the front evaporator only.
Electronic cycling clutch switch is connected in series with
mode control switch, high pressure cut-out switch, low pressure cut-
out switch, and PCM. The electronic cycling clutch switch opens when
refrigerant temperature is below about 37
F (2.8C) and will close
when refrigerant temperature is about 40F (4.4C).
FIXED ORIFICE TUBE
Dakota & Ram Pickup
The fixed orifice tube is located in outlet line of the
condenser. The orifice tube inlet and outlet ends have a screen to

filter the refrigerant. The orifice tube is used to meter the flow of
liquid refrigerant into the evaporator core.
HIGH PRESSURE CUT-OUT SWITCH
High pressure cut-out switch is located on compressor
discharge line, near compressor. On Dakota and Ram Pickup, it is
connected in series with the clutch cycling pressure switch and
control panel, between ground and PCM.
On Durango, it is connected in series with the electronic
cycling clutch switch, low pressure cut-out switch and control panel,
between ground and PCM. PCM controls compressor clutch operation.
On all models, when discharge pressure reaches 450-490 psi
(31.6-34.5 kg/cm
), high pressure cut-out switch interrupts A/C
request signal to PCM. PCM de-energizes compressor clutch relay,
disengaging compressor clutch. When discharge pressure drops to 270-
330 psi (23.2-19 kg/cm
) switch will close, thus restoring A/C request
signal to PCM.
HIGH PRESSURE RELIEF VALVE
High pressure relief valve is located on compressor manifold.
Valve vents system pressure if pressure is greater than 500-600 psi
(35.1-42.2 kg/cm
). Valve will reset when pressure decreases to 400
psi (28.1 kg/cm).
LOW PRESSURE CUT-OUT SWITCH OPERATION
Durango
Low pressure cut-out switch is located on suction line near
firewall. It is connected in series with the electronic cycling clutch
switch, high pressure cut-out switch and control panel, between ground
and PCM. PCM controls compressor clutch operation.
When discharge pressure reaches 10 psi (.7 kg/cm
), switch
interrupts A/C request signal to PCM. PCM de-energizes compressor
clutch relay, disengaging compressor clutch. When discharge pressure
increases to 13-27 psi (.9-1.9 kg/cm
), switch will close thus
restoring A/C request signal to PCM.
ADJUSTMENTS
TEMPERATURE CONTROL CABLE ADJUSTMENT
Dakota & Durango
1) Ensure temperature control cable housing and core are
connected at both A/C-heater control panel and A/C-heater assembly.
Ensure A/C-heater control panel is installed.
2) Rotate temperature control knob so that knob pointer is at
12 o'clock position. Pull temperature control knob straight out from
A/C-heater control panel until perimeter of knob (not knob pointer)
protrudes about .25" (6 mm) from face of A/C-heater control panel.
3) Rotate temperature control knob clockwise so that knob
pointer is at one o'clock position. Push in on knob slightly and
continue rotating knob to its full clockwise stop. Place knob pointer
at a position about .32" (8 mm) beyond end of Red stripe. Release
knob. If knob is pointing at about .32" (8 mm) beyond end of Red
stripe, go to next step. If knob is not pointing at about .32" (8 mm)
beyond end of Red stripe, go back to step 2) and repeat adjustment
procedure.
4) Rotate temperature control knob counterclockwise so that
knob pointer is at 12 o'clock position. Push temperature control knob
straight into A/C-heater control panel until perimeter of knob (not

knob pointer) is flush with base of A/C-heater control panel.
5) Rotate temperature control knob to its full clockwise
stop. Release knob. Knob pointer should be aimed at end of Red stripe.
If knob is pointed at end of Red stripe, go to next step. If knob is
not pointed at end of Red stripe, go back to step 2) and repeat
adjustment procedure.
6) Rotate temperature control knob to its full
counterclockwise stop. Release knob. If knob springs back, self-
adjuster clip securing temperature control cable to blend-air door
lever is improperly installed. See TEMPERATURE CONTROL CABLE R & I. If
knob does not spring back, temperature control cable adjustment is
complete.
TESTING
* PLEASE READ THIS FIRST *
WARNING: To avoid injury from accidental air bag deployment, read and
carefully follow all SERVICE PRECAUTIONS and DISABLING &
ACTIVATING AIR BAG SYSTEM procedures in AIR BAG SYSTEM SAFETY
article.
A/C-HEATER CONTROL PANEL TEST
1) Connect a vacuum gauge in line with Black A/C-heater
vacuum supply hose, located at tee near power brake booster (Dakota)
or in engine compartment (Durango and Ram Pickup). Position gauge so
it can be viewed from passenger compartment.
2) Start engine. While observing gauge, rotate mode control
knob to each mode position (one position at a time). Pause after each
selection. Test gauge should drop, then return to 8 in. Hg shortly
after each selection is made. If gauge reading is as specified, go to
next step. If gauge reading is not as specified, check for vacuum leak
in vacuum lines or A/C-heater control panel.
3) Move temperature control knob quickly to full hot and full
cold positions. A distinct sound of blend-air door hitting its stops
should be heard. No spring-back of knob should exist.
4) If temperature control knob operates as specified,
temperature control system is okay. On Dakota and Durango, if
temperature control knob does not operate as specified, check
condition, routing, installation, and adjustment of temperature
control cable. See TEMPERATURE CONTROL CABLE ADJUSTMENT . Also check
blend air door for proper installation, obstructions, or faulty seals.
A/C SYSTEM PERFORMANCE
1) Park vehicle out of direct sunlight. Ensure ambient
temperature is at least 70F (21C). Connect tachometer and manifold
gauge set to vehicle. Turn A/C on. Turn mode control to panel and
recirculated air positions, temperature control lever to maximum
cooling, and blower to high.
2) Start engine and allow it to run at 1000 RPM, with A/C
compressor clutch engaged. Engine should be at operating temperature
with doors, windows, and hood closed. Insert thermometer into left
center air outlet.
3) Run engine and operate system for 5 minutes. The A/C
compressor clutch may cycle, depending on temperature. If A/C
compressor clutch cycles, stop engine and disconnect negative battery
cable. Remove clutch cycling pressure switch connector. Place a jumper
wire across terminals of clutch cycling pressure switch harness
connector.
4) Connect negative battery cable. Turn A/C on. Start and

operate engine at idle speed. With A/C compressor clutch engaged, note
air outlet temperature, compressor discharge pressure, and evaporator
inlet pressure. See appropriate A/C SYSTEM PERFORMANCE TEMPERATURE
SPECIFICATIONS and A/C SYSTEM PERFORMANCE PRESSURE SPECIFICATIONS
tables.
A/C SYSTEM PERFORMANCE TEMPERATURE SPECIFICATIONS (DAKOTA)









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Ambient Temp. F (C) Outlet Vent Temp. F (C)
70 (21) ..................................................... 38 (3\
)
80 (27) ..................................................... 44 (7\
)
90 (32) ..................................................... 48 (9\
)
100 (38) ................................................... 55 (13\
)
110 (43) ................................................... 64 (18\
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A/C SYSTEM PERFORMANCE TEMPERATURE SPECIFICATIONS (DURANGO)








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Ambient Temp. F (C) Outlet Vent Temp. F (C)
70 (21) ..................................................... 48 (9\
)
80 (27) ..................................................... 48 (9\
)
90 (32) .................................................... 54 (12\
)
100 (38) ................................................... 59 (15\
)
110 (43) ................................................... 65 (18\
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A/C SYSTEM PERFORMANCE TEMPERATURE SPECIFICATIONS (RAM PICKUP)








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Ambient Temp. F (C) Outlet Vent Temp. F (C)
70 (21) ................................................ 40-45 (5-7\
)
80 (27) .............................................. 55-60 (13-16\
)
90 (32) .............................................. 60-70 (16-21\
)
100 (38) ............................................. 70-75 (21-24\
)
110 (43) ............................................. 80-85 (27-29\
)
120 (49) ............................................. 85-90 (29-32\
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A/C SYSTEM PERFORMANCE PRESSURE SPECIFICATIONS (DAKOTA)








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Ambient Temp. High Side Low SideF (C) psi (kg/cm) psi (kg/cm)
70 (21) .............. 160-200 (11.2-14.1) ....... 25-35 (1.8-2\
.5)
80 (27) .............. 190-220 (13.4-15.5) ....... 32-40 (2.2-2\
.8)
90 (32) .............. 200-240 (14.1-16.9) ....... 37-45 (2.6-3\
.2)
100 (38) ............. 220-260 (15.5-18.3) ....... 39-50 (2.7-3\
.5)
110 (43) ............. 250-300 (17.6-21.1) ....... 45-55 (3.2-3\
.9)









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A/C SYSTEM PERFORMANCE PRESSURE SPECIFICATIONS (DURANGO)








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Ambient Temp. High Side Low SideF (C) psi (kg/cm) psi (kg/cm)
70 (21) .............. 100-150 (7.0-10.5) ........ 20-30 (1.4-2\
.1)
80 (27) .............. 135-185 (9.5-13.0) ........ 20-30 (1.4-2\
.1)
90 (32) .............. 170-220 (12.0-15.5) ....... 25-35 (1.8-2\
.5)
100 (38) ............. 210-255 (14.8-17.9) ....... 31-41 (2.2-2\
.9)
110 (43) ............. 245-295 (17.2-20.7) ....... 37-47 (2.6-3\
.3)









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A/C SYSTEM PERFORMANCE PRESSURE SPECIFICATIONS (RAM PICKUP)








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Ambient Temp. High Side Low SideF (C) psi (kg/cm) psi (kg/cm)
70 (21) .............. 135-145 (9.5-10.2) ........ 35-40 (2.5-2\
.8)
80 (27) .............. 175-215 (12.3-15.1) ....... 40-50 (2.8-3\
.5)
90 (32) .............. 215-270 (15.1-19.0) ....... 50-60 (3.5-4\
.2)
100 (38) ............. 270-330 (19.0-23.2) ....... 60-70 (4.2-4\
.9)
110 (43) ............. 340-370 (23.9-26.0) ....... 70-80 (4.9-5\
.6)
120 (49) ............. 400-430 (28.1-30.2) ....... 85-90 (6.0-6\
.3)









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BLOWER MOTOR RELAY, HIGH SPEED BLOWER MOTOR RELAY &
COMPRESSOR CLUTCH RELAY
NOTE: Relays appear different, but testing procedures for blower
motor, high speed blower motor, and compressor clutch relays
are identical.
1) Front blower motor relay and compressor clutch relay are
located in Power Distribution Center (PDC). On Durango, high speed
blower motor relay is located in fuse/relay block under left side of
instrument panel.
2) Disconnect negative battery cable. Remove blower motor or
compressor clutch relay. Using an ohmmeter, check for continuity
between terminals No. 87A and 30 of relay. See Fig. 1 or 2. If
continuity does not exist, replace relay. If continuity exists, go to
next step.
3) Using an ohmmeter, check for continuity between terminals
No. 30 and 87 of relay. If continuity exists, replace relay. If
continuity does not exist, go to next step.
4) Measure resistance between terminals No. 85 and 86 of
relay. Reading should be 70-80 ohms. If reading is not as specified,
replace relay. If reading is as specified, go to next step.
5) Using jumper wires, connect battery voltage to terminal
No. 86 and ground terminal No. 85. See Fig. 1 or 2. Check that
continuity exists between terminals No. 30 and 87. Check that
continuity does not exist between terminals No. 87A and 30. If
continuity is not as specified, replace relay. If continuity is as
specified, relay is okay.
Fig. 1: Identifying Blower Motor Relay Terminals (Typical)
Courtesy of Chrysler Corp.

Fig. 2: Identifying Compressor Clutch Relay Terminals (Typical)
Courtesy of Chrysler Corp.
BLOWER MOTOR RESISTOR
1) Disconnect negative battery cable. Disconnect blower motor
resistor harness connector. Using an ohmmeter, check for continuity
between all 4 front blower motor resistor terminals, or 3 rear blower
motor resistor terminals. If continuity exists, go to next step. If
continuity does not exist, replace faulty blower motor resistor.
2) Check for open or short in circuits between blower motor
resistor and A/C-heater control panel. Also check for open or short in
wire between blower motor resistor and blower motor.
BLOWER MOTOR SWITCH
Front
1) Using a voltmeter, check underhood power distribution
center for battery voltage at fuse No. 5 (40-amp) on Dakota and
Durango, or fuse No. 5 (40-amp) on Ram Pickup. If battery voltage
exists, go to next step. If battery voltage does not exist, check for
open in Red wire between battery and underhood power distribution
center. If Red wire is okay, replace underhood power distribution
center.
2) Disconnect negative battery cable. Remove A/C-heater
control panel. See A/C-HEATER CONTROL PANEL R & I . Disconnect A/C-
heater control panel harness connector. Using an ohmmeter, check for
continuity between A/C-heater control panel harness connector terminal
No. 7 (Black wire on Dakota and Durango; Black/Orange on Ram Pickup)
and ground. If continuity exists, go to step 4).
3) If continuity does not exist, repair open in Black or
Black/Orange wire between A/C-heater control panel harness connector
terminal No. 7 and ground connector located at lower right corner of
instrument panel (Dakota and Durango) or behind center of instrument
panel (Ram Pickup).
4) Place mode control knob to any position except OFF. Using
an ohmmeter, check for continuity between A/C-heater control panel
connector terminal No. 7 and terminals No. 3, 4, 5, and 6 while
rotating blower motor switch. See Fig. 3.
5) If continuity does not exist at any terminal, replace
faulty A/C-heater control panel. If continuity exists as specified,
check for open in circuits between A/C-heater control panel and blower
motor resistor. Also check for an open in circuit between A/C-heater

control panel and blower motor.
Fig. 3: Identifying Blower Motor Switch Connector Terminals (Typical)\
Courtesy of Chrysler Corp.
Rear (Durango)
1) Disconnect negative battery cable. Remove rear blower
motor switch located in headliner. See BLOWER MOTOR SWITCH (REAR)
under REMOVAL & INSTALLATION. Disconnect rear blower motor switch
connector. Using an ohmmeter, check continuity between rear blower
motor switch connector Black wire and ground. If continuity exists, go
to next step. If continuity does not exist, repair open in Black wire
between rear blower motor switch connector and ground connector
located at left rear of vehicle body.
2) Place blower motor switch knob to any position except OFF.
Using an ohmmeter, check for continuity between rear blower motor
switch connector Black wire and Black/Light Blue wire, and
Black/Orange wire and Dark Green wire while rotating blower motor
switch.
3) If continuity does not exist at any terminal, replace
faulty blower motor switch. If continuity exists as specified, check
for open in circuits between blower motor switch and blower motor
resistor. Also check for an open in circuit between blower motor
switch connector and blower motor relay.
CLUTCH CYCLING PRESSURE SWITCH
Dakota & Ram Pickup
1) Locate clutch cycling pressure switch on side or top of
A/C accumulator. Ensure clutch cycling pressure switch is properly
installed on A/C accumulator fitting. Ensure system pressure is
correct. See A/C SYSTEM PERFORMANCE test.
2) Start and run engine with A/C on. If clutch cycles, turn
engine off and disconnect negative battery cable. Disconnect clutch
cycling pressure switch connector. Place a jumper wire across
terminals of clutch cycling pressure switch harness connector. Connect
negative battery cable. Connect manifold gauge set. Set A/C-heater

controls to A/C. Start and operate engine at idle speed.
3) Using an ohmmeter, check for continuity between switch
terminals. Continuity should exist when suction pressure reading is
above 38 psi (2.7 kg/cm
) on Dakota; 43 psi (3.0 kg/cm) on Ram
Pickup. Continuity should not exist when suction pressure reading
drops below 20.5 psi (1.4 kg/cm
) on Dakota; 25 psi (1.8 kg/cm) on
Ram Pickup. If switch is okay, test and repair clutch control circuit
as needed. If switch is not okay, replace faulty clutch cycling
pressure switch.
ELECTRONIC CYCLING CLUTCH SWITCH
Durango
1) Locate electronic cycling clutch switch on thermal
expansion valve in engine compartment. Ensure system pressure is
correct. See A/C SYSTEM PERFORMANCE test. Ensure low pressure cut-out
switch and high pressure cut-out switch are working properly. See
LOW PRESSURE CUT-OUT SWITCH TEST and HIGH PRESSURE CUT-OUT SWITCH
test.
2) Disconnect negative battery cable. Disconnect electronic
cycling clutch switch and high pressure cut-out switch connectors.
Using an ohmmeter, check for continuity in Light Green/White wire
between electronic cycling clutch switch and high pressure cut-out
switch. If continuity exists in Light Green/White wire, go to next
step. If continuity does not exist in Light Green/White wire, repair
wire as necessary.
3) Disconnect low pressure cut-out switch connector. Using an
ohmmeter, check for continuity in Dark Blue/Yellow wire between
electronic cycling clutch switch and low pressure cut-out switch. If
continuity exists in Dark Blue/Yellow wire, go to next step. If
continuity does not exist in Dark Blue/Yellow wire, repair wire as
necessary.
4) Connect low pressure cut-out switch and high pressure cut-
out switch connectors. Connect negative battery cable. Turn ignition
on. Using voltmeter, check for battery voltage at electronic cycling
clutch switch connector terminal No. 2 (White wire). If battery
voltage exists, go to step 6).
5) If battery voltage does not exist, check fuse No. 7 (15-
amp) at junction block located at bottom left of instrument panel. If
fuse is okay, check for short or open in White wire between electronic
cycling clutch switch connector and fuse No. 7 (15-amp) at junction
block.
6) Connect electronic cycling clutch switch connector. Ensure
ambient temperature is between 68-90
F (20-30C). Start engine and
turn A/C on. If compressor clutch cycles 2-3 times per minute, replace
faulty electronic cycling clutch switch. If compressor clutch does not
cycle, check PCM for proper operation. See appropriate G - TESTS
W/CODES article in ENGINE PERFORMANCE section.
HIGH PRESSURE CUT-OUT SWITCH
1) Locate high pressure cut-out switch on compressor
discharge line, near compressor. Ensure system pressure is correct.
See A/C SYSTEM PERFORMANCE test. Disconnect negative battery cable.
Disconnect high pressure cut-off switch connector.
2) Using an ohmmeter, check for continuity between switch
terminals. If continuity exists, test and repair clutch control
circuit as needed. If continuity does not exist, replace faulty
switch.
LOW PRESSURE CUT-OUT SWITCH TEST
Durango