heating DODGE RAM 2002 Service Owners Manual

A/C Diagnosis
Condition Possible Causes Correction
2. Refrigerant flow
through the accumulator
is restricted.2. (Refer to Plumbing/Accumulator/ Removal/Installation)
in this group. Replace the restricted accumulator, if
required.
3. Refrigerant flow
through the a/c
evaporator is restricted.3. (Refer to Plumbing/A/C Evaporator/ Removal/
Installation) in this group. Replace the restricted
evaporator, if required.
4. Faulty compressor. 4. (Refer to Plumbing/A/C Compressor/ Removal/
Installation) in this group. Replace the compressor, if
required.
LOW SIDE PRESSURE
IS NORMAL OR
SLIGHTLY HIGH, AND
HIGH SIDE PRESSURE
IS TOO HIGH.1. Condenser air flow
restricted.1. Check the condenser for damaged fins, foreign objects
obstructing air flow through the condenser fins, and
missing or improperly installed air seals. Refer to Cooling
for more information on air seals. Clean, repair, or replace
components as required.
2. Inoperative cooling
fan.2. Refer to Cooling for more information. Test the cooling
fan and replace, if required.
3. Refrigerant system
overcharged.3. (Refer to Plumbing/Standard Procedure - Refrigerant
System Charge) in this group. Recover the refrigerant
from the refrigerant system. Charge the refrigerant
system to the proper level, if required.
4. Air in the refrigerant
system.4. (Refer to Plumbing/Diagnosis and Testing - Refrigerant
System Leaks) in this group. Test the refrigerant system
for leaks. Repair, evacuate and charge the refrigerant
system, if required.
5. Engine overheating. 5. Refer to Cooling for more information. Test the cooling
system and repair, if required.
LOW SIDE PRESSURE
IS TOO HIGH, AND
HIGH SIDE PRESSURE
IS TOO LOW.1. Accessory drive belt
slipping.1. Refer to Cooling for more information. Inspect the
accessory drive belt condition and tension. Tighten or
replace the accessory drive belt, if required.
2. A/C orifice tube not
installed.2. (Refer to Plumbing/A/C Orifice Tube/Diagnosis and
Testing) in this group. Replace the liquid line, if required.
3. Faulty a/c compressor. 3. (Refer to Plumbing/A/C Compressor/ Removal/
Installation) in this group. Replace the compressor, if
required.
LOW SIDE PRESSURE
IS TOO LOW, AND HIGH
SIDE PRESSURE IS
TOO HIGH.1. Restricted refrigerant
flow through the
refrigerant lines.1. (Refer to Plumbing/Caution - Refrigerant Hoses/Lines/
Tubes Precautions) in this group. Inspect the refrigerant
lines for kinks, tight bends or improper routing. Correct
the routing or replace the refrigerant line, if required.
2. Restricted refrigerant
flow through the a/c
orifice tube.2. (Refer to Plumbing/A/C Orifice Tube/Diagnosis and
Testing) in this group. Replace the liquid line, if required.
3. Restricted refrigerant
flow through the a/c
condenser.3. (Refer to Plumbing/A/C Condenser/ Removal/
Installation) in this group. Replace the restricted a/c
condenser, if required.
BR/BEHEATING & AIR CONDITIONING 24 - 5
HEATING & AIR CONDITIONING (Continued)

DIAGNOSIS AND TESTING - HEATER
PERFORMANCE
Before performing the following tests, refer to Cool-
ing for the procedures to check the engine coolant
level and flow, engine coolant reserve/recovery sys-
tem operation, accessory drive belt condition and ten-
sion, radiator air flow and the fan drive operation.
Also be certain that the accessory vacuum supply
line is connected at the engine vacuum source.
MAXIMUM HEATER OUTPUT
Engine coolant is delivered to the heater core
through two heater hoses. With the engine idling atnormal operating temperature, set the temperature
control knob in the full hot position, the mode control
switch knob in the floor position, and the blower
motor switch knob in the highest speed position.
Using a test thermometer, check the temperature of
the air being discharged at the HVAC housing floor
outlets. Compare the test thermometer reading to the
Temperature Reference chart.
Temperature Reference
Ambient Air Temperature15.5É C
(60É F)21.1É C
(70É F)26.6É C
(80É F)32.2É C
(90É F)
Minimum Air Temperature at
Floor Outlet62.2É C
(144É F)63.8É C
(147É F)65.5É C
(150É F)67.2É C
(153É F)
If the floor outlet air temperature is too low, refer
to Cooling to check the engine coolant temperature
specifications. Both of the heater hoses should be hot
to the touch. The coolant return heater hose should
be slightly cooler than the coolant supply heater
hose. If the return hose is much cooler than the sup-
ply hose, locate and repair the engine coolant flow
obstruction in the cooling system. Refer to Cooling
for the procedures.
An alternate method of checking heater perfor-
mance is to use a DRBIIItscan tool to monitor the
engine coolant temperature. The floor outlet air tem-
perature reading should be no more than 4.5É C (40É
F) lower than the engine coolant temperature read-
ing.
OBSTRUCTED COOLANT FLOW Possible loca-
tions or causes of obstructed coolant flow:
²Faulty water pump.
²Faulty thermostat.
²Pinched or kinked heater hoses.
²Improper heater hose routing.
²Plugged heater hoses or supply and return ports
at the cooling system connections.
²A plugged heater core.If proper coolant flow through the cooling system is
verified, and heater outlet air temperature is still
low, a mechanical problem may exist.
MECHANICAL PROBLEMS Possible locations or
causes of insufficient heat:
²An obstructed cowl air intake.
²Obstructed heater system outlets.
²A faulty, obstructed or improperly installed
blend door.
²A faulty blower system.
²A faulty a/c heater control.
TEMPERATURE CONTROL
If the heater outlet air temperature cannot be
adjusted with the temperature control knob on the
a/c heater control panel, the following could require
service:
²A faulty a/c heater control.
²A faulty blend door actuator.
²A faulty, obstructed or improperly installed
blend door.
²An obstructed cowl air intake.
²The engine cooling system.
Heater Diagnosis
CONDITION POSSIBLE CAUSE CORRECTION
INSUFFICIENT HEATER
OUTPUT.1. Incorrect engine
coolant level.1. Check the engine coolant level. Refer to Cooling for
the procedures.
2. Air trapped in engine
cooling system.2. Check the operation of the coolant reserve/recovery
system. Refer to Cooling for the procedures.
24 - 6 HEATING & AIR CONDITIONINGBR/BE
HEATING & AIR CONDITIONING (Continued)

Heater Diagnosis
3. Incorrect engine
coolant temperature.3. Check the performance and operation of the engine
cooling system including: thermostat, water pump, fan
drive, accessory drive belt, coolant flow (plugged radiator
or heater core, plugged or kinked coolant hoses), air flow
(missing or improperly installed radiator air seals or fan
shroud). Refer to Cooling for the procedures.
4. Blend door actuator
inoperative or defective.4. (Refer to Controls/Blend Door Actuator) in this group.
5. Blend door not
operating properly.5. Check for a damaged, obstructed or improperly
installed blend door or seals. (Refer to Controls/Blend
Door Actuator) in this group.
6. Insufficient air flow
through heater housing.6. Remove foreign material or obstructions from cowl air
intake.
7. Improper blower motor
operation.7. (Refer to Distribution/Blower Motor/ Diagnosis and
Testing) in this group.
STANDARD PROCEDURE - DIODE
REPLACEMENT
(1) Disconnect the battery negative cable and iso-
late it.
(2) Locate the diode in the harness, and remove
the protective covering.
(3) Remove the diode from the harness, pay atten-
tion to the current flow direction (Fig. 3).
(4) Remove the insulation from the wires in the
harness. Only remove enough insulation to solder in
the new diode.
(5) Install the new diode in the harness, making
sure current flow is correct. If necessary refer to the
appropriate wiring diagram for current flow.
(6) Solder the connection together using rosin core
type solder only.Do not use acid core solder.(7) Tape the diode to the harness using electrical
tape making, sure the diode is completely sealed
from the elements.
(8) Re-connect the battery negative cable, and test
affected systems.
SPECIFICATIONS
A/C APPLICATION TABLE
Item Description Notes
Vehicle BR/BE - Ram
Pickup
System R134a w/orifice
tube
Compressor Sanden SD7H15 SP-20 PAG oil
Freeze±up
ControlA/C Low
Pressure Switchaccumulator
mounted
Low psi Control opens < 22-24
psi resets >
37-43 psi
High psi Control switch - opens >
450 - 490 psi,
resets < 270 -
330 psimounted on
discharge line,
near
compressor
A/C Heater
Control Headmanual type
Mode Door vacuum actuator
Blend Door electric actuator
Recirculation
Doorvacuum actuator
Fig. 3 DIODE IDENTIFICATION
1 - CURRENT FLOW
2 - BAND AROUND DIODE INDICATES CURRENT FLOW
3 - DIODE AS SHOWN IN THE DIAGRAMS
BR/BEHEATING & AIR CONDITIONING 24 - 7
HEATING & AIR CONDITIONING (Continued)

Item Description Notes
Blower Motor hardwired to
control headresistor block
Cooling Fan viscous fan
Clutch
Control relay PCM
Draw 2 - 3.9 amps @
12V  0.5V @ 70É
FItem Description Notes
Gap 0.0169- 0.0319
DRB IIIT
Reads TPS, RPM, A/C
switch test
Actuators clutch relay
TORQUE SPECIFICATIONS
TORQUE SPECIFICATIONS
DESCRIPTION N´m Ft. Lbs. In. Lbs.
A/C COMPRESSOR
CLUTCH PLATE NUT14.4 10.5 12.7
A/C COMPRESOR LINE
MANIFOLD FASTENER22 16 195
A/C COMPRESSOR TO
MOUNTING BRACKET
BOLTS24 17.7 212
ACCUMULATOR
RETAINING BAND4.5 3.3 40
BLOWER MOTOR
SCREWS2.2 1.6 20
CHECK VALVE AND
NIPPLE UNIT (DIESEL)24 18 212
CONDENSER MOUNTING
SCREWS/NUTS10.5 7.7 93
DISCHARGE LINE TO
CONDENSER FASTENER20 14.8 177
DOOR ACTUATOR
SCREWS2.2 1.6 19.5
HVAC HOUSING SCREWS 2.2 1.6 19.5
HVAC HOUSING TO DASH
PANEL NUTS (ENGINE
SIDE)7 5.2 62
HVAC HOUSING TO DASH
PANEL NUTS
(PASSENGER
COMPARTMENT SIDE)4.5 3.3 40
24 - 8 HEATING & AIR CONDITIONINGBR/BE
HEATING & AIR CONDITIONING (Continued)

CONTROLS
DIAGNOSIS AND TESTING - VACUUM SYSTEM
Vacuum control is used to operate the mode doors
in the heater-only and HVAC housings. Testing of the
heater-only and a/c heater mode control switch oper-
ation will determine if the vacuum, electrical, and
mechanical controls are functioning. However, it is
possible that a vacuum control system that operates
perfectly at engine idle (high engine vacuum) may
not function properly at high engine speeds or loads
(low engine vacuum). This can be caused by leaks in
the vacuum system, or by a faulty or improperly
installed vacuum check valve.
A vacuum system test will help to identify the
source of poor vacuum system performance or vac-
uum system leaks. Before starting this test, stop the
engine and make certain that the problem is not a
disconnected vacuum supply tube at the engine vac-
uum source or the vacuum reservoir.
Use an adjustable vacuum test set (Special Tool
C-3707) and a suitable vacuum pump to test the
HVAC vacuum control system. With a finger placed
over the end of the vacuum test hose probe (Fig. 1),
adjust the bleed valve on the test set gauge to obtain
a vacuum of exactly 27 kPa (8 in. Hg.). Release and
block the end of the probe several times to verify that
the vacuum reading returns to the exact 27 kPa (8
in. Hg.) setting. Otherwise, a false reading will be
obtained during testing.
VACUUM CHECK VALVE
(1) Remove the vacuum check valve. On gasoline
engines, one valve is located in the vacuum supply
tube (black) at the intake manifold tap on the right
side of the engine. A second check valve is located
next to the tee fitting in the vacuum supply tube
(black) near the dash panel in the engine compart-
ment. On diesel engines, the vacuum check valve is
integral to the engine vacuum pump nipple and is
threaded into the vacuum pump. The vacuum check
valve must be removed in order to perform the fol-
lowing tests. (Refer to 24 - HEATING & AIR CONDI-
TIONING/CONTROLS/VACUUM CHECK VALVE -
REMOVAL)
(2) Connect the test set vacuum supply hose to the
a/c heater control side of the valve. When connected
to this side of the check valve, no vacuum should
pass and the test set gauge should return to the 27
kPa (8 in. Hg.) setting. If OK, go to step Step 3. If
not OK, replace the faulty valve.
(3) Connect the test set vacuum supply hose to the
engine vacuum side of the valve. When connected to
this side of the check valve, vacuum should flow
through the valve without restriction. If not OK,
replace the faulty valve.
A/C HEATER CONTROLS
(1) Connect the test set vacuum probe to the
HVAC vacuum supply (black) tube in the engine com-
partment. Position the test set gauge so that it can
be viewed from the passenger compartment.
(2) Place the a/c heater mode control switch knob
to each mode position, one position at a time, and
pause after each selection. The test set gauge should
return to the 27 kPa (8 in. Hg.) setting shortly after
each selection is made. If not OK, a component or
vacuum line in the vacuum circuit of the selected
mode has a leak. See Locating Vacuum Leaks below.
CAUTION: Do not use lubricant on the switch ports
or in the holes in the plug, as lubricant will ruin the
vacuum valve in the switch. A drop of clean water
in the connector plug holes will help the connector
slide onto the switch ports.
Fig. 1 ADJUST VACUUM TEST BLEED VALVE
1 - VACUUM PUMP TOOL C-4289
2 - VACUUM TEST SET C-3707
3 - BLEED VALVE
4 - PROBE
24 - 10 CONTROLSBR/BE

remove the refrigerant lines or fittings. (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING/A/C
COMPRESSOR - REMOVAL)
(3) Unplug the compressor clutch coil wire harness
connector.
(4) Insert the two pins of the spanner wrench
(Special Tool 6462 in Kit 6460) into the holes of the
clutch plate. Hold the clutch plate stationary and
remove the hex nut (Fig. 5).
(5) Remove the clutch plate and clutch shims. On
models with the diesel engine option, a puller (Spe-
cial Tool 6461 in Kit 6460) is used to remove the
clutch plate (Fig. 6). This compressor also uses a
shaft key, which must be removed.(6) Remove the external front housing snap ring
with snap ring pliers (Fig. 7).
(7) Install the lip of the rotor puller (Special Tool
C-6141-1 in Kit 6460) into the snap ring groove
exposed in Step 6, and install the shaft protector
(Special Tool C-6141-2 in Kit 6460) (Fig. 8).
Fig. 5 CLUTCH NUT REMOVE
1 - FRONT PLATE SPANNER
Fig. 6 CLUTCH PULLER - DIESEL MODELS
1 - FRONT PLATE
2 - PULLER
Fig. 7 EXTERNAL SNAP RING REMOVE
1 - EXTERNAL SNAP RING
Fig. 8 SHAFT PROTECTOR AND PULLER
1 - PULLER SHAFT PROTECTOR
2-JAWS
24 - 14 CONTROLSBR/BE
A/C COMPRESSOR CLUTCH (Continued)

NOTE: The air gap is determined by the spacer
shims. When installing an original, or a new clutch
assembly, try the original shims first. When install-
ing a new clutch onto a compressor that previously
did not have a clutch, use 1.0, 0.50, and 0.13 milli-
meter (0.040, 0.020, and 0.005 inch) shims from the
clutch hardware package that is provided with the
new clutch.
(12) On models with the diesel engine option,
install the compressor on the engine. (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING/A/C
COMPRESSOR - INSTALLATION)
(13) Connect the battery negative cable.
A/C COMPRESSOR CLUTCH
RELAY
DESCRIPTION
The a/c compressor clutch relay is a International
Standards Organization (ISO) micro-relay. The termi-
nal designations and functions are the same as a con-
ventional ISO relay. However, the micro-relay
terminal orientation (footprint) is different, the cur-
rent capacity is lower, and the relay case dimensions
are smaller than those of the conventional ISO relay.
OPERATION
The compressor clutch relay is a electromechanical
device that switches battery current to the compres-
sor clutch coil when the Powertrain Control Module
(PCM) grounds the coil side of the relay. The PCM
responds to inputs from the a/c heater control, the a/closs of charge switch, the a/c pressure transducer and
the evaporator fin probe.
The compressor clutch relay is located in the Power
Distribution Center (PDC) in the engine compart-
ment. Refer to the PDC label for relay identification
and location.
The compressor clutch relay cannot be repaired
and, if faulty or damaged, it must be replaced.
DIAGNOSIS AND TESTING - A/C COMPRESSOR
CLUTCH RELAY
RELAY TEST
The compressor clutch relay (Fig. 16) is located in
the Power Distribution Center (PDC). Refer to the
PDC label for relay identification and location.
Remove the relay from the PDC to perform the fol-
lowing tests:
(1) A relay in the de-energized position should
have continuity between terminals 87A and 30, and
no continuity between terminals 87 and 30. If OK, go
to Step 2. If not OK, replace the faulty relay.
(2) Resistance between terminals 85 and 86 (elec-
tromagnet) should be 75   5 ohms. If OK, go to Step
3. If not OK, replace the faulty relay.
(3) Connect a battery to terminals 85 and 86.
There should now be continuity between terminals
30 and 87, and no continuity between terminals 87A
and 30. If OK, see the Relay Circuit Test below. If not
OK, replace the faulty relay.
RELAY CIRCUIT TEST
For circuit descriptions and diagrams, (Refer to
Appropriate Wiring Information).
Fig. 15 CHECK CLUTCH AIR GAP
1 - FEELER GAUGE
Fig. 16 COMPRESSOR CLUTCH RELAY
TERMINAL LEGEND
NUMBER IDENTIFICATION
30 COMMON FEED
85 COIL GROUND
86 COIL BATTERY
87 NORMALLY OPEN
87A NORMALLY CLOSED
BR/BECONTROLS 24 - 17
A/C COMPRESSOR CLUTCH (Continued)

(3) On vehicles with air conditioning, turn the
temperature control knob to the extreme counter
clockwise (Cool) position, and set the mode control
switch knob to the Bi-Level (A/C) position. The out-
side (recirculation) air door should be open to outside
air. If not OK, (Refer to 24 - HEATING & AIR CON-
DITIONING/CONTROLS - DIAGNOSIS AND TEST-
ING - VACUUM SYSTEM).
(4) Open the vehicle windows. Test the blower
motor operation in all speeds. If not OK, (Refer to 24
- HEATING & AIR CONDITIONING/DISTRIBU-
TION/BLOWER MOTOR - DIAGNOSIS AND TEST-
ING).
(5) On vehicles with air conditioning, the compres-
sor should be running and the air conditioning sys-
tem in operation unless the ambient air temperature
is below about -1É C (30É F). If not OK, (Refer to 24 -
HEATING & AIR CONDITIONING - DIAGNOSIS
AND TESTING - A/C PERFORMANCE).
(6) Check the mode control switch operation. The
heater and air conditioner systems should respond as
described in the owner's manual in the vehicle glove
box to each mode selected. Reduce the engine speed
to normal idle. The vacuum will be high at low idle
and the vacuum actuators should respond quickly. If
not OK, (Refer to 24 - HEATING & AIR CONDI-
TIONING/CONTROLS - DIAGNOSIS AND TEST-
ING - VACUUM SYSTEM).
(7) If the vacuum tests, and the electrical compo-
nent and circuit tests reveal no problems, disassem-
ble the HVAC housing to inspect for mechanical
misalignment or binding of the mode doors (Refer to
24 - HEATING & AIR CONDITIONING/DISTRIBU-
TION/HVAC HOUSING - DISASSEMBLY)
REMOVAL
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISO-
LATE THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYS-
TEM CAPACITOR TO DISCHARGE BEFORE PER-
FORMING FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN AN ACCIDENTAL
AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
(1) Disconnect and isolate the battery negative
cable.
(2) Reach under the instrument panel near the
driver side of the floor panel transmission tunnel andunplug the a/c heater control to HVAC housing vac-
uum harness connector.
(3) While still reaching under the instrument
panel, disengage the retainer on the a/c heater con-
trol half of the vacuum harness from the hole in the
center distribution duct (Fig. 18).
(4) Remove the cluster bezel from the instrument
panel(Refer to 23 - BODY/INSTRUMENT PANEL/
CLUSTER BEZEL - REMOVAL).
(5) Remove the four screws that secure the a/c
heater control to the instrument panel (Fig. 19).
(6) Pull the a/c heater control assembly away from
the instrument panel far enough to access the con-
nections on the back of the control.
(7) Unplug the wire harness connector from the
back of the a/c heater control.
(8) On vehicles with heated mirrors, unplug the
heated mirror wire harness connector from the back
of the a/c heater control.
(9) Remove the a/c heater control from the instru-
ment panel.
INSTALLATION
(1) Plug the wire harness connector(s) into the
receptacle(s) on the back of the a/c heater control.
(2) Route the HVAC vacuum harness through the
hole in the reinforcement below the a/c heater control
opening of the instrument panel.
(3) Position the a/c heater control in the instru-
ment panel and secure it with four screws. Tighten
the screws to 2.2 N´m (20 in. lbs.).
Fig. 18 A/C HEATER CONTROL VACUUM HARNESS
ROUTING
1 - A/C HEATER CONTROL VACUUM HARNESS
2 - REINFORCEMENT
3 - RETAINER
4 - CENTER DISTRIBUTION DUCT
BR/BECONTROLS 24 - 19
A/C-HEATER CONTROL (Continued)

(4) Reinstall the cluster bezel to the instrument
panel(Refer to 23 - BODY/INSTRUMENT PANEL/
CLUSTER BEZEL - INSTALLATION).
(5) Reach under the instrument panel to reinstall
the a/c heater control vacuum harness retainer to the
side of the center distribution duct.
(6) Plug in the two halves of the a/c heater control
to HVAC housing vacuum harness connector.
(7) Connect the battery negative cable.
A/C HIGH PRESSURE SWITCH
DESCRIPTION
The a/c high pressure switch is located on the dis-
charge line near the compressor. The switch is
screwed onto a fitting that contains a Schrader-type
valve, which allows the switch to be serviced without
discharging the refrigerant system. The discharge
line fitting is equipped with an O-ring to seal the
switch connection.
OPERATION
The a/c high pressure switch is connected in series
electrically with the a/c low pressure switch between
ground and the Powertrain Control Module (PCM).
The switch contacts open and close causing the PCM
to turn the compressor clutch on and off. This pre-
vents compressor operation when the discharge line
pressure approaches high levels.
The a/c high pressure switch contacts are open
when the discharge line pressure rises above about3100 to 3375 kPa (450 to 490 psi). The switch con-
tacts will close when the discharge line pressure
drops to about 1860 to 2275 kPa (270 to 330 psi).
When checking refrigerant system pressures with a
manifold gauge set, keep in mind that the indicated
pressures will be about 172 kpa (25 psi) below the
actual switch pressure values due to the pressure
drop that occurs in the refrigerant system between
the switch and the high pressure service port.
The a/c high pressure switch is a factory-calibrated
unit. The switch 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 - DIAGNOSIS AND
TESTING)
For circuit descriptions and diagrams, (Refer to
Appropriate Wiring Information).
(1) Disconnect and isolate the battery negative
cable.
(2) Unplug the a/c high pressure switch wire har-
ness connector from the switch on the refrigerant
system fitting.
(3) On the four terminal high pressure switch,
check for continuity between terminals C and D. On
the two terminal switch, check for continuity
between both terminals of the a/c high pressure
switch. There should be continuity. If OK, test and
repair the A/C switch sense circuit as required. If not
OK, replace the faulty switch.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Unplug the wire harness connector from the a/c
high pressure switch, which is mounted to a fitting
on the discharge line between the compressor and
the condenser inlet.
(3) Unscrew the a/c high pressure switch from the
discharge line fitting.
(4) Remove the a/c high pressure switch from the
vehicle.
(5) Remove the O-ring seal from the discharge line
fitting and discard.
INSTALLATION
(1) Lubricate a new O-ring seal with clean refrig-
erant oil and install it on the discharge line 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 com-
pressor in the vehicle. (Refer to 24 - HEATING &
Fig. 19 A/C HEATER CONTROL REMOVE/INSTALL
1 - HEATED MIRROR WIRE HARNESS CONNECTOR
2 - WIRE HARNESS CONNECTOR
3 - SCREW
4 - HEATER-A/C CONTROL
24 - 20 CONTROLSBR/BE
A/C-HEATER CONTROL (Continued)

AIR CONDITIONING/PLUMBING/REFRIGERANT
OIL - DESCRIPTION)
(2) Install and tighten the high pressure cut-off
switch on the discharge line fitting. The switch
should be hand-tightened onto the discharge line fit-
ting.
(3) Plug the wire harness connector into the high
pressure cut-off switch.
(4) Connect the battery negative cable.
A/C LOW PRESSURE SWITCH
DESCRIPTION
The a/c low pressure switch is located on the top of
the accumulator. The switch is screwed onto an accu-
mulator fitting that contains a Schrader-type valve,
which allows the switch to be serviced without dis-
charging the refrigerant system. The accumulator fit-
ting is equipped with an O-ring to seal the switch
connection.
OPERATION
The a/c low pressure switch is connected in series
electrically with the a/c high pressure switch and the
a/c heater control, between ground and the Power-
train Control Module (PCM). The switch contacts
open and close causing the PCM to turn the compres-
sor clutch on and off. This regulates the refrigerant
system pressure and controls evaporator tempera-
ture. Controlling evaporator temperature prevents
condensate water on the evaporator fins from freez-
ing and obstructing air conditioning system air flow.
The a/c low pressure switch contacts are open
when the suction pressure is about 152-165 kPa
(22-24 psi) or lower. The switch contacts will close
when the suction pressure rises to about 255-296 kPa
(37-43 psi) or above. Lower ambient temperatures,
below about -1É C (30É F), will also cause the switch
contacts to open. This is due to the pressure/temper-
ature relationship of the refrigerant in the system.
The a/c low pressure switch is a factory-calibrated
unit. It cannot be adjusted or repaired and, if faulty
or damaged, it must be replaced.
DIAGNOSIS AND TESTING - A/C LOW
PRESSURE SWITCH
Before performing diagnosis of the a/c low pressure
switch, be certain that the switch is properly
installed on the accumulator fitting. If the switch is
too loose it may not open the Schrader-type valve in
the accumulator fitting, which will prevent the
switch from correctly monitoring the refrigerant sys-
tem pressure. Also verify that the refrigerant system
has the correct refrigerant charge. (Refer to 24 -HEATING & AIR CONDITIONING - DIAGNOSIS
AND TESTING - A/C PERFORMANCE)
Remember that lower ambient temperatures, below
about -1É C (30É F), during cold weather will open the
switch contacts and prevent compressor operation
due to the pressure/temperature relationship of the
refrigerant. For circuit descriptions and diagrams,
(Refer to Appropriate Wiring Information).
(1) Disconnect and isolate the battery negative
cable.
(2) Unplug the a/c low pressure switch wire har-
ness connector from the switch on the accumulator
fitting.
(3) Install a jumper wire between the two cavities
of the a/c low pressure switch wire harness connector.
(4) Connect a manifold gauge set to the refrigerant
system service ports. (Refer to 24 - HEATING & AIR
CONDITIONING/PLUMBING - STANDARD PRO-
CEDURE - REFRIGERANT SYSTEM SERVICE
EQUIPMENT)
(5) Connect the battery negative cable.
(6) Place the a/c heater mode control switch knob
in any A/C position and start the engine.
(7) Check for continuity between the two terminals
of the low pressure cycling clutch switch. There
should be continuity with a suction pressure reading
of 296 kPa (43 psi) or above, and no continuity with a
suction pressure reading of 172 kPa (25 psi) or below.
If OK, test and repair the A/C switch sense circuit as
required. If not OK, replace the faulty switch.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Unplug the wire harness connector from the a/c
low pressure switch on the top of the accumulator
(Fig. 20).
(3) Unscrew the a/c low pressure switch from the
fitting on the top of the accumulator.
(4) Remove the O-ring seal from the accumulator
fitting and discard.
INSTALLATION
(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 com-
pressor in the vehicle. (Refer to 24 - HEATING &
AIR CONDITIONING/PLUMBING/REFRIGERANT
OIL - DESCRIPTION)
(2) Install and tighten the a/c low pressure switch
on the accumulator fitting. The switch should be
hand-tightened onto the accumulator fitting.
(3) Plug the wire harness connector into the a/c
low pressure switch.
BR/BECONTROLS 24 - 21
A/C HIGH PRESSURE SWITCH (Continued)