2000 DODGE NEON heater

Pending ConditionsÐThere are not conditions
or situations that prompt conflict or suspension of
testing. The oxygen sensor heater test is not run
pending resolution of MIL illumination due to oxygen
sensor failure.
SuspendÐThere are no conditions which exist for
suspending the Heater Monitor.
CATALYST MONITOR
To comply with clean air regulations, vehicles are
equipped with catalytic converters. These converters
reduce the emission of hydrocarbons, oxides of nitro-
gen and carbon monoxide.
Normal vehicle miles or engine misfire can cause a
catalyst to decay. A meltdown of the ceramic core can
cause a reduction of the exhaust passage. This can
increase vehicle emissions and deteriorate engine
performance, driveability and fuel economy.
The catalyst monitor uses dual oxygen sensors
(O2S's) to monitor the efficiency of the converter. The
dual O2S strategy is based on the fact that as a cat-
alyst deteriorates, its oxygen storage capacity and its
efficiency are both reduced. By monitoring the oxy-
gen storage capacity of a catalyst, its efficiency can
be indirectly calculated. The upstream O2S is used to
detect the amount of oxygen in the exhaust gas
before the gas enters the catalytic converter. The
PCM calculates the A/F mixture from the output of
the O2S. A low voltage indicates high oxygen content
(lean mixture). A high voltage indicates a low content
of oxygen (rich mixture).
When the upstream O2S detects a lean condition,
there is an abundance of oxygen in the exhaust gas.
A functioning converter would store this oxygen so it
can use it for the oxidation of HC and CO. As the
converter absorbs the oxygen, there will be a lack of
oxygen downstream of the converter. The output of
the downstream O2S will indicate limited activity in
this condition.
As the converter loses the ability to store oxygen,
the condition can be detected from the behavior of
the downstream O2S. When the efficiency drops, no
chemical reaction takes place. This means the con-
centration of oxygen will be the same downstream as
upstream. The output voltage of the downstream
O2S copies the voltage of the upstream sensor. The
only difference is a time lag (seen by the PCM)
between the switching of the O2S's.
To monitor the system, the number of lean-to-rich
switches of upstream and downstream O2S's is
counted. The ratio of downstream switches to
upstream switches is used to determine whether the
catalyst is operating properly. An effective catalyst
will have fewer downstream switches than it has
upstream switches i.e., a ratio closer to zero. For atotally ineffective catalyst, this ratio will be one-to-
one, indicating that no oxidation occurs in the device.
The system must be monitored so that when cata-
lyst efficiency deteriorates and exhaust emissions
increase to over the legal limit, the MIL (check
engine lamp) will be illuminated.
Monitor OperationÐTo monitor catalyst effi-
ciency, the PCM expands the rich and lean switch
points of the heated oxygen sensor. With extended
switch points, the air/fuel mixture runs richer and
leaner to overburden the catalytic converter. Once
the test is started, the air/fuel mixture runs rich and
lean and the O2 switches are counted. A switch is
counted when an oxygen sensor signal goes from
below the lean threshold to above the rich threshold.
The number of Rear O2 sensor switches is divided by
the number of Front O2 sensor switches to determine
the switching ratio.
The test runs for 20 seconds. As catalyst efficiency
deteriorated over the life of the vehicle, the switch
rate at the downstream sensor approaches that of the
upstream sensor. If at any point during the test
period the switch ratio reaches a predetermined
value, a counter is incremented by one. The monitor
is enabled to run another test during that trip. When
the test fails three times, the counter increments to
three, a malfunction is entered, and a Freeze Frame
is stored. When the counter increments to three dur-
ing the next trip, the code is matured and the MIL is
illuminated. If the test passes the first, no further
testing is conducted during that trip.
The MIL is extinguished after three consecutive
good trips. The good trip criteria for the catalyst
monitor is more stringent than the failure criteria. In
order to pass the test and increment one good trip,
the downstream sensor switch rate must be less than
80% of the upstream rate (60% for manual transmis-
sions). The failure percentages are 90% and 70%
respectively.
Enabling ConditionsÐThe following conditions
must typically be met before the PCM runs the cat-
alyst monitor. Specific times for each parameter may
be different from engine to engine.
²Accumulated drive time
²Enable time
²Ambient air temperature
²Barometric pressure
²Catalyst warm-up counter
²Engine coolant temperature
²Accumulated throttle position sensor
²Vehicle speed
²MAP
²RPM
²Engine in closed loop
²Fuel level
25 - 22 EMISSION CONTROL SYSTEMSPL
DESCRIPTION AND OPERATION (Continued)

Pending ConditionsÐ
²Misfire DTC
²Front Oxygen Sensor Response
²Front Oxygen Sensor Heater Monitor
²Front Oxygen Sensor Electrical
²Rear Oxygen Sensor Rationality (middle check)
²Rear Oxygen Sensor Heater Monitor
²Rear Oxygen Sensor Electrical
²Fuel System Monitor
²All TPS faults
²All MAP faults
²All ECT sensor faults
²Purge flow solenoid functionality
²Purge flow solenoid electrical
²All PCM self test faults
²All CMP and CKP sensor faults
²All injector and ignition electrical faults
²Idle Air Control (IAC) motor functionality
²Vehicle Speed Sensor
²Brake switch
²Intake air temperature
ConflictÐThe catalyst monitor does not run if
any of the following are conditions are present:
²EGR Monitor in progress
²Fuel system rich intrusive test in progress
²EVAP Monitor in progress
²Time since start is less than 60 seconds
²Low fuel level
²Low ambient air temperature
SuspendÐThe Task Manager does not mature a
catalyst fault if any of the following are present:
²Oxygen Sensor Monitor, Priority 1
²Upstream Oxygen Sensor Heater, Priority 1
²EGR Monitor, Priority 1
²EVAP Monitor, Priority 1
²Fuel System Monitor, Priority 2
²Misfire Monitor, Priority 2
NON-MONITORED CIRCUITS
OPERATION
The PCM does not monitor all circuits, systems
and conditions that could have malfunctions causing
driveability problems. However, problems with these
systems may cause the PCM to store diagnostic trou-
ble codes for other systems or components. For exam-
ple, a fuel pressure problem will not register a fault
directly, but could cause a rich/lean condition or mis-
fire. This could cause the PCM to store an oxygen
sensor or misfire diagnostic trouble code.
The major non-monitored circuits are listed below
along with examples of failures modes that do not
directly cause the PCM to set a DTC, but for a sys-
tem that is monitored.FUEL PRESSURE
The fuel pressure regulator controls fuel system
pressure. The PCM cannot detect a clogged fuel
pump inlet filter, clogged in-line fuel filter, or a
pinched fuel supply or return line. However, these
could result in a rich or lean condition causing the
PCM to store an oxygen sensor or fuel system diag-
nostic trouble code.
SECONDARY IGNITION CIRCUIT
The PCM cannot detect an inoperative ignition coil,
fouled or worn spark plugs, ignition cross firing, or
open spark plug cables.
CYLINDER COMPRESSION
The PCM cannot detect uneven, low, or high engine
cylinder compression.
EXHAUST SYSTEM
The PCM cannot detect a plugged, restricted or
leaking exhaust system. It may set a EGR or Fuel
system fault or O2S.
FUEL INJECTOR MECHANICAL MALFUNCTIONS
The PCM cannot determine if a fuel injector is
clogged, the needle is sticking or if the wrong injector
is installed. However, these could result in a rich or
lean condition causing the PCM to store a diagnostic
trouble code for either misfire, an oxygen sensor, or
the fuel system.
EXCESSIVE OIL CONSUMPTION
Although the PCM monitors engine exhaust oxygen
content when the system is in closed loop, it cannot
determine excessive oil consumption.
THROTTLE BODY AIR FLOW
The PCM cannot detect a clogged or restricted air
cleaner inlet or filter element.
VACUUM ASSIST
The PCM cannot detect leaks or restrictions in the
vacuum circuits of vacuum assisted engine control
system devices. However, these could cause the PCM
to store a MAP sensor diagnostic trouble code and
cause a high idle condition.
PCM SYSTEM GROUND
The PCM cannot determine a poor system ground.
However, one or more diagnostic trouble codes may
be generated as a result of this condition. The mod-
ule should be mounted to the body at all times, also
during diagnostic.
PLEMISSION CONTROL SYSTEMS 25 - 23
DESCRIPTION AND OPERATION (Continued)

(3) Remove seat back.
(4) Remove track and recliner assembly.
(5) Remove seat cushion (Fig. 5).
INSTALLATION
(1) Connect seat cushion heater element connector,
if equipped.
(2) Install track and recliner assembly. Tighten
bolts to 12 N´m (9 ft. lbs.) torque.
(3) Install seat back. Tighten bolts to 40 N´m (30
ft. lbs.) torque.
(4) Install cushion side shields.
(5) Install seat in vehicle.
REAR SEAT BACK
REMOVAL
(1) Remove rear seat cushion.
(2) Remove bolts attaching rear seat back and seat
belts to floor.
(3) Push rear seat back upward to disengage hooks
at top of seat back (Fig. 6).
(4) Remove rear seat from vehicle.
INSTALLATION
(1) Move rear seat back into position in vehicle.
(2) Push seat back downward to engage hooks at
top of seat back.
(3) Install bolts attaching rear seat back and seat
belts to floor.
NOTE: The torque specification for the inner seat
belt/rear seat back retaining bolts is 57 N´m (42 ft.
lbs.).
(4) Install rear seat cushion.
Fig. 5 Front Seat Cushion
1 ± FRONT SEAT CUSHION
Fig. 6 Rear Seat Back
1 ± REAR SEAT BACK
2 ± REAR OUTER RIGHT SEAT BELT
3 ± REAR INNER LEFT SEAT BELT
4 ± REAR INNER RIGHT SEAT BELT
23 - 10 BODYPL
REMOVAL AND INSTALLATION (Continued)

DIAGNOSIS AND TESTING
WATER LEAKS
Water leaks can be caused by poor sealing,
improper body component alignment, body seam
porosity, missing plugs, or blocked drain holes. Cen-
trifugal and gravitational force can cause water to
drip from a location away from the actual leak point,
making leak detection difficult. All body sealing
points should be water tight in normal wet-driving
conditions. Water flowing downward from the front of
the vehicle should not enter the passenger or luggage
compartment. Moving sealing surfaces will not
always seal water tight under all conditions. At
times, side glass or door seals will allow water to
enter the passenger compartment during high pres-
sure washing or hard driving rain (severe) condi-
tions. Overcompensating on door or glass
adjustments to stop a water leak that occurs under
severe conditions can cause premature seal wear and
excessive closing or latching effort. After completing
a repair, water-test vehicle to verify leak has stopped
before returning vehicle to use.
VISUAL INSPECTION BEFORE WATER LEAK TESTS
Verify that floor and body plugs are in place, body
drains are clear, and body components are properly
aligned and sealed. If component alignment or seal-
ing is necessary, refer to the appropriate section of
this group for proper procedures.
WATER LEAK TESTS
WARNING: DO NOT USE ELECTRIC SHOP LIGHTS
OR TOOLS IN WATER TEST AREA. PERSONAL
INJURY CAN RESULT.
When the conditions causing a water leak have
been determined, simulate the conditions as closely
as possible.
²If a leak occurs with the vehicle parked in a
steady light rain, flood the leak area with an open-
ended garden hose.
²If a leak occurs while driving at highway speeds
in a steady rain, test the leak area with a reasonable
velocity stream or fan spray of water. Direct the
spray in a direction comparable to actual conditions.
²If a leak occurs when the vehicle is parked on an
incline, hoist the end or side of the vehicle to simu-
late this condition. This method can be used when
the leak occurs when the vehicle accelerates, stops or
turns. If the leak occurs on acceleration, hoist the
front of the vehicle. If the leak occurs when braking,
hoist the back of the vehicle. If the leak occurs on left
turns, hoist the left side of the vehicle. If the leak
occurs on right turns, hoist the right side of the vehi-cle. For hoisting recommendations refer to Group 0,
Lubrication and Maintenance, General Information
section.
WATER LEAK DETECTION
To detect a water leak point-of-entry, do a water
test and watch for water tracks or droplets forming
on the inside of the vehicle. If necessary, remove inte-
rior trim covers or panels to gain visual access to the
leak area. If the hose cannot be positioned without
being held, have someone help do the water test.
Some water leaks must be tested for a considerable
length of time to become apparent. When a leak
appears, find the lowest point of the water track or
drop. After leak point has been found, repair the leak
and water test to verify that the leak has stopped.
Locating the entry point of water that is leaking
into a cavity between panels can be difficult. The
trapped water may splash or run from the cavity,
often at a distance from the entry point. Most water
leaks of this type become apparent after accelerating,
stopping, turning, or when on an incline.
MIRROR INSPECTION METHOD
When a leak point area is visually obstructed, use
a suitable mirror to gain visual access. A mirror can
also be used to deflect light to a limited-access area
to assist in locating a leak point.
BRIGHT LIGHT LEAK TEST METHOD
Some water leaks in the luggage compartment can
be detected without water testing. Position the vehi-
cle in a brightly lit area. From inside the darkened
luggage compartment inspect around seals and body
seams. If necessary, have a helper direct a drop light
over the suspected leak areas around the luggage
compartment. If light is visible through a normally
sealed location, water could enter through the open-
ing.
PRESSURIZED LEAK TEST METHOD
When a water leak into the passenger compart-
ment cannot be detected by water testing, pressurize
the passenger compartment and soap test exterior of
the vehicle. To pressurize the passenger compart-
ment, close all doors and windows, start engine, and
set heater control to high blower in HEAT position. If
engine can not be started, connect a charger to the
battery to ensure adequate voltage to the blower.
With interior pressurized, apply dish detergent solu-
tion to suspected leak area on the exterior of the
vehicle. Apply detergent solution with spray device or
soft bristle brush. If soap bubbles occur at a body
seam, joint, seal or gasket, the leak entry point could
be at that location.
23 - 18 BODYPL

HEATING AND AIR CONDITIONING
TABLE OF CONTENTS
page page
GENERAL INFORMATION
A/C APPLICATION TABLE...................2
HEATER AND AIR CONDITIONING CONTROL...2
HEATER AND AIR CONDITIONING............2
INTRODUCTION..........................3
SAFETY PRECAUTIONS AND WARNINGS......4
DESCRIPTION AND OPERATION
A/C REFRIGERANT LINES..................4
BLOWER MOTOR RESISTOR................5
COMPRESSOR...........................5
COMPRESSOR FRONT SHAFT SEAL..........6
CONDENSATION DRAIN TUBE...............6
ENGINE COOLING SYSTEM REQUIREMENTS...6
EVAPORATOR PROBE......................6
HANDLING TUBING AND FITTINGS...........6
HIGH PRESSURE CUT OUT SWITCH..........6
LOW PRESSURE CUT OFF SWITCH..........6
SIDE WINDOW DEMISTERS................7
SYSTEM AIRFLOW........................7
SYSTEM OIL LEVEL.......................7
VACUUM CONTROL SYSTEM................8
DIAGNOSIS AND TESTING
A/C PERFORMANCE TEST..................9
BLOWER MOTOR ELECTRICAL DIAGNOSIS....9
BLOWER MOTOR VIBRATION AND/OR
NOISE DIAGNOSIS.....................11
COMPRESSOR NOISE DIAGNOSIS..........11
EVAPORATOR PROBE TEST................11
EXPANSION VALVE.......................11
HEATER PERFORMANCE TEST.............13
LOW PRESSURE CUT OFF SWITCH.........14
SYSTEM CHARGE LEVEL TEST.............14
VACUUM CONTROL SYSTEM...............15
SERVICE PROCEDURES
CHARGING A/C SYSTEM..................17EVACUATING REFRIGERANT SYSTEM........18
R-134a REFRIGERANT....................19
SERVICING REFRIGERANT OIL LEVEL.......19
SYSTEM LEAK CHECKING.................20
REMOVAL AND INSTALLATION
A/C FILTER/DRIER.......................20
A/C SERVICE PORT VALVE CORES..........21
BLOWER MOTOR AND WHEEL ASSEMBLY....21
BLOWER MOTOR RESISTOR...............22
BLOWER MOTOR WHEEL.................22
COMPRESSOR..........................22
COMPRESSOR CLUTCH/COIL ASSEMBLY.....23
CONDENSATION DRAIN TUBE..............25
CONDENSER............................25
DISCHARGE LINE........................26
EVAPORATOR...........................26
EVAPORATOR PROBE.....................26
EXPANSION VALVE.......................27
HEATER CORE..........................28
HEATER HOSES.........................28
HIGH PRESSURE CUT OUT SWITCH.........29
HIGH PRESSURE RELIEF VALVE............29
LIQUID LINE............................29
LOW PRESSURE CUT OFF SWITCH.........29
MODE CONTROL CABLE..................30
RECIRCULATION DOOR ACTUATOR.........31
SUCTION LINE..........................31
TEMPERATURE CONTROL CABLE...........32
UNIT HOUSING..........................32
DISASSEMBLY AND ASSEMBLY
HEATER-A/C HOUSING....................34
ADJUSTMENTS
MODE CONTROL CABLE..................34
TEMPERATURE CONTROL CABLE...........34
PLHEATING AND AIR CONDITIONING 24 - 1

GENERAL INFORMATION
A/C APPLICATION TABLE
Item Description Notes
Vehicle PL Neon
System expansion valve
Total Refrigerant
CapacityR134a 765 grams / 27 oz / 1.69 lbs
Total Oil Capacity ND-8 PAG oil 180 ml / 6.10 oz
Compressor Nippondenso 10S17
Freeze-up Control Fin sensor-3 wire input to PCM, evaporator mounted, cycles
clutch off below 34É F, cycles back on
above 45É F
Low psi Control opens < 14 psi, resets > 38 psi expansion valve mounted
High psi Control opens > 470 psi, resets < 370 - 330 psi compressor mounted switch
Control head manual type
Mode Door cable
Blend Air Door cable
Fresh/Recirc door vacuum actuator
Blower Motor control head switched resistor block
Cooling Fan variable speed PCM controlled ISO solid state fan relay
Clutch
Control relay PCM
Draw 2.5 amps @ 12V60.5V @ 70É F
Gap 0.014º - 0.0269
DRB IIIT
Reads TPS, RPM, A/C switch test, fin sensor
A/C & fan relays
Actuators fan & clutch relays
HEATER AND AIR CONDITIONING CONTROL
Both the heater-only and heater-A/C systems use a
combination of, electrical, cable, and vacuum con-
trols. These controls provide the vehicle operator
with a number of setting options to help control the
climate and comfort within the vehicle. Refer to the
owner's manual in the vehicle glove box for more
information on the features, use, and suggested oper-
ation of these controls.
The heater-only or heater-A/C control panel is located
to the right of the instrument cluster on the instrument
panel. The control panel contains rotary-type knobs.
There is a blower motor speed switch, mode control
switch, temperature control, and airflow control.
The heater-only or heater-A/C control panel cannot
be repaired. If faulty or damaged, the entire unit
must be replaced. The control knobs and the illumi-
nation lamps are available for service replacement.
HEATER AND AIR CONDITIONING
All vehicles are equipped with a common heater-
A/C housing assembly (Fig. 1). The system combines
air conditioning, heating, and ventilating capabilities
in a single unit housing mounted under the instru-
ment panel. On heater-only systems, the evaporator
coil is omitted from the housing and replaced with an
air restrictor plate.
Outside air enters the vehicle through the cowl top
opening at the base of the windshield, and passes
through a plenum chamber to the heater-A/C system
blower housing. Air flow velocity can then be
adjusted with the blower motor speed selector switch
on the heater-A/C control panel. The air intake open-
ings must be kept free of snow, ice, leaves, and other
obstructions for the heater-A/C system to receive a
sufficient volume of outside air.
24 - 2 HEATING AND AIR CONDITIONINGPL

It is also important to keep the air intake openings
clear of debris because leaf particles and other debris
that is small enough to pass through the cowl ple-
num screen can accumulate within the heater-A/C
housing. The closed, warm, damp and dark environ-
ment created within the heater-A/C housing is ideal
for the growth of certain molds, mildews and other
fungi. Any accumulation of decaying plant matter
provides an additional food source for fungal spores,
which enter the housing with the fresh air. Excess
debris, as well as objectionable odors created by
decaying plant matter and growing fungi can be dis-
charged into the passenger compartment during
heater-A/C system operation.
The heater and optional air conditioner are blend-
air type systems. In a blend-air system, a blend-air
door controls the amount of unconditioned air (or
cooled air from the evaporator on models with air
conditioning) that is allowed to flow through, or
around, the heater core. A temperature control knob
on the heater-A/C control panel determines the dis-
charge air temperature by moving a cable, which
operates the blend-air door. This allows an almost
immediate manual control of the output air tempera-
ture of the system.
The mode control knob on the heater-only or heat-
er-A/C control panel is used to direct the conditioned
air to the selected system outlets. The mode control
switch uses a cable to control the mode door, while
the recirculation air door is operated by a vacuum
actuator motor.On air conditioned vehicles, the outside air intake
can be shut off by selecting the recirculation mode
(Recirc) with the mode control knob. This will oper-
ate a vacuum actuated recirculating air door that
closes off the outside fresh air intake and recirculates
the air that is already inside the vehicle.
The optional air conditioner for all models is
designed for the use of non-CFC, R-134a refrigerant.
The air conditioning system has an evaporator to cool
and dehumidify the incoming air prior to blending it
with the heated air. This air conditioning system
uses an evaporator probe to maintain minimum
evaporator temperature and prevent evaporator
freezing, and cycles the compressor clutch.
INTRODUCTION
Both the heater and the heater/air conditioning
systems share many of the same functioning compo-
nents. This group will deal with both systems
together when component function is common, and
separately when they are not.
For proper operation of the instrument panel con-
trols, refer to the Owner's Manual provided with the
vehicle.
To service the heater core or evaporator, the unit
housing must be removed from the vehicle (Fig. 2).Fig. 1 Common Blend-Air HVAC (Heating,
Ventilation, Air Conditioning) System - Typical
1 ± TEMPERATURE BLEND/AIR DOOR
2 ± EVAPORATOR CORE
3 ± BLOWER
4 ± PANEL DEFROST DOOR
5 ± HEAT DEFROST DOOR
6 ± HEATER CORE
7 ± RECIRCULATING AIR DOOR
Fig. 2 HVAC Unit Housing
1 ± AIR DISTRIBUTION
2 ± RECIRCULATION DOOR VACUUM ACTUATOR
3 ± AIR INLET
4 ± BLOWER MOTOR
5 ± EVAPORATOR PROBE CONNECTOR
6 ± CONTROL CABLES
7 ± VACUUM HARNESS
PLHEATING AND AIR CONDITIONING 24 - 3
GENERAL INFORMATION (Continued)

COMPRESSOR FRONT SHAFT SEAL
The compressor front shaft seal is not serviceable.
If a leak is detected at the shaft seal, the compressor
must be replaced as a unit.
CONDENSATION DRAIN TUBE
Condensation that accumulates in the evaporator
housing is drained from a tube through the dash and
on to the ground. This tube must be kept open to
prevent condensate water from collecting in the bot-
tom of the housing.
The tapered end of the drain tube is designed to
keep contaminants from entering the heater A/C unit
housing. If the tube is pinched or blocked, condensate
cannot drain, causing water to back up and spill into
the passenger compartment. It is normal to see con-
densate drainage below the vehicle. If the tube is
damaged, it should be replaced.
ENGINE COOLING SYSTEM REQUIREMENTS
To maintain ample temperature levels from the
heating-A/C system, the cooling system must be in
proper working order. Refer to Group 0, Lubrication
and Maintenance or Group 7, Cooling System of this
manual.
The use of a bug screen is not recommended. Any
obstructions forward of the condenser can reduce the
effectiveness of the air conditioning system.
EVAPORATOR PROBE
The evaporator probe can be replaced without hav-
ing to remove the unit housing from the vehicle.
The evaporator probe is located in the unit housing
and placed in the evaporator fins. The probe prevents
evaporator freeze-up. This is done by cycling the com-
pressor clutch OFF when evaporator temperature
drops below freeze point. It cycles ON when the
evaporator temperature rises above freeze point. The
evaporator probe uses a thermistor probe in a capil-
lary tube. The tube is inserted between the evapora-
tor fins in the heater-A/C unit housing.
HANDLING TUBING AND FITTINGS
Kinks in the refrigerant tubing or sharp bends in
the refrigerant hose lines will greatly reduce the
capacity of the entire system. High pressures are pro-
duced in the system when it is operating. Extreme
care must be exercised to make sure that all connec-
tions are pressure tight. Dirt and moisture can enter
the system when it is opened for repair or replace-
ment of lines or components. The refrigerant oil will
absorb moisture readily out of the air. This moisture
will convert into acids within a closed system.CAUTION: The system must be completely empty
before opening any fitting or connection in the
refrigeration system. Open fittings with caution
even after the system has been emptied. If any
pressure is noticed as a fitting is loosened,
retighten fitting and evacuate the system again.
A good rule for the flexible hose lines is to keep
the radius of all bends at least 10 times the diame-
ter of the hose. Sharper bends will reduce the flow
of refrigerant. The flexible hose lines should be
routed so they are at least 3 inches (80 mm) from
the exhaust manifold. Inspect all flexible hose lines
to make sure they are in good condition and prop-
erly routed.
The use of correct wrenches when making con-
nections is very important. Improper wrenches or
improper use of wrenches can damage the fittings.
The internal parts of the A/C system will remain
stable as long as moisture-free refrigerant and
refrigerant oil is used. Abnormal amounts of dirt,
moisture or air can upset the chemical stability.
This may cause operational troubles or even seri-
ous damage if present in more than very small
quantities.
When opening a refrigeration system, have every-
thing you will need to repair the system ready. This
will minimize the amount of time the system must
be opened. Cap or plug all lines and fittings as
soon as they are opened. This will help prevent the
entrance of dirt and moisture. All new lines and
components should be capped or sealed until they
are ready to be used.
All tools, including the refrigerant dispensing
manifold, the manifold gauge set, and test hoses
should be kept clean and dry.
HIGH PRESSURE CUT OUT SWITCH
The high pressure cut out switch is located on the
rear of the compressor (Fig. 7). It turns off the com-
pressor if the system pressure exceeds 3240 kPa (470
psi).
LOW PRESSURE CUT OFF SWITCH
The Low Pressure Cut Off Switch (Fig. 8) monitors
the refrigerant gas pressure on the suction side of
the system. The low pressure cut off switch is located
on the expansion valve. The low pressure cut off
switch turns off voltage to the compressor clutch coil
when refrigerant gas pressure drops to levels that
could damage the compressor. The low pressure cut
out switch is a sealed factory calibrated unit. It must
be replaced if defective.
24 - 6 HEATING AND AIR CONDITIONINGPL
DESCRIPTION AND OPERATION (Continued)