gas type DODGE RAM 2003 Service Manual Online

CAUTION
SERVICE CAUTIONS
CAUTION: Liquid refrigerant is corrosive to metal
surfaces. Follow the operating instructions supplied
with the service equipment being used.
Never add R-12 to a refrigerant system designed to
use R-134a. Damage to the system will result.
R-12 refrigerant oil must not be mixed with R-134a
refrigerant oil. They are not compatible.
Do not use R-12 equipment or parts on the R-134a
system. Damage to the system will result.
Do not overcharge the refrigerant system. This will
cause excessive compressor head pressure and
can cause noise and system failure.
Recover the refrigerant before opening any fitting
or connection. Open the fittings with caution, even
after the system has been discharged. Never open
or loosen a connection before recovering the refrig-
erant.
Do not remove the secondary retention clip from
any spring-lock coupler connection while the refrig-
erant system is under pressure. Recover the refrig-
erant before removing the secondary retention clip.
Open the fittings with caution, even after the sys-
tem has been discharged. Never open or loosen a
connection before recovering the refrigerant.
The refrigerant system must always be evacuated
before charging.
Do not open the refrigerant system or uncap a
replacement component until you are ready to ser-
vice the system. This will prevent contamination in
the system.
Before disconnecting a component, clean the out-
side of the fittings thoroughly to prevent contami-
nation from entering the refrigerant system.
Immediately after disconnecting a component from
the refrigerant system, seal the open fittings with a
cap or plug.
Before connecting an open refrigerant fitting,
always install a new seal or gasket. Coat the fitting
and seal with clean refrigerant oil before connect-
ing.
Do not remove the sealing caps from a replacement
component until it is to be installed.
When installing a refrigerant line, avoid sharp
bends that may restrict refrigerant flow. Position the
refrigerant lines away from exhaust system compo-
nents or any sharp edges, which may damage the
line.
Tighten refrigerant fittings only to the specified
torque. The aluminum fittings used in the refriger-
ant system will not tolerate overtightening.
When disconnecting a refrigerant fitting, use a
wrench on both halves of the fitting. This will pre-vent twisting of the refrigerant lines or tubes.
Refrigerant oil will absorb moisture from the atmo-
sphere if left uncapped. Do not open a container of
refrigerant oil until you are ready to use it. Replace
the cap on the oil container immediately after using.
Store refrigerant oil only in a clean, airtight, and
moisture-free container.
Keep service tools and the work area clean. Con-
tamination of the refrigerant system through care-
less work habits must be avoided.
CAUTION - REFRIGERANT HOSES/LINES/
TUBES PRECAUTIONS
Kinks or sharp bends in the refrigerant plumbing
will reduce the capacity of the entire system. High
pressures are produced in the system when it is oper-
ating. Extreme care must be exercised to make sure
that all refrigerant system connections are pressure
tight.
A good rule for the flexible hose refrigerant lines is
to keep the radius of all bends at least ten times the
diameter of the hose. Sharp bends will reduce the
flow of refrigerant. The flexible hose lines should be
routed so they are at least 80 millimeters (3 inches)
from the exhaust manifold. It is a good practice to
inspect all flexible refrigerant system hose lines at
least once a year to make sure they are in good con-
dition and properly routed.
There are two types of refrigerant fittings:
²All fittings with O-rings need to be coated with
refrigerant oil before installation. Use only O-rings
that are the correct size and approved for use with
R-134a refrigerant. Failure to do so may result in a
leak.
²Unified plumbing connections with gaskets can-
not be serviced with O-rings. The gaskets are not
reusable and new gaskets do not require lubrication
before installing.
Using the proper tools when making a refrigerant
plumbing connection is very important. Improper
tools or improper use of the tools can damage the
refrigerant fittings. Always use two wrenches when
loosening or tightening tube fittings. Use one wrench
to hold one side of the connection stationary, while
loosening or tightening the other side of the connec-
tion with a second wrench.
The refrigerant must be recovered completely from
the system before opening any fitting or connection.
Open the fittings with caution, even after the refrig-
erant has been recovered. If any pressure is noticed
as a fitting is loosened, tighten the fitting and
recover the refrigerant from the system again.
Do not discharge refrigerant into the atmosphere.
Use an R-134a refrigerant recovery/recycling device
that meets SAE Standard J2210.
DRPLUMBING 24 - 33
PLUMBING (Continued)

INSTALLATION
INSTALLATION
WARNING: REVIEW THE WARNINGS AND CAU-
TIONS IN THE FRONT OF THIS SECTION BEFORE
PERFORMING THE FOLLOWING OPERATION.
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - WARNING) (Refer to 24 - HEATING &
AIR CONDITIONING/PLUMBING - CAUTION) (Refer
to 24 - HEATING & AIR CONDITIONING/PLUMBING -
CAUTION - REFRIGERANT HOSES/LINES/TUBES
PRECAUTIONS)
The compressor may be removed and repositioned
without disconnecting the refrigerant lines or dis-
charging the refrigerant system. Discharging is not
necessary if servicing the compressor clutch or clutch
coil, the engine, the cylinder head, or the generator.
NOTE: If a replacement compressor is being
installed, be certain to check the refrigerant oil
level. (Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING/REFRIGERANT OIL - STANDARD PRO-
CEDURE - REFRIGERANT OIL LEVEL) Use only
refrigerant oil of the type recommended for the
compressor in the vehicle. (Refer to 24 - HEATING &AIR CONDITIONING/PLUMBING/REFRIGERANT OIL -
DESCRIPTION)
(1) Install the compressor to the mounting bracket.
(2) On the 3.7L, 4.7L, 5.7L and 8.0L gasoline
engines install and tighten the bolts in the following
sequence (Fig. 4):
²The number one bolt (rear) is hand tightened
first then tightened to 55 N´m (41 ft. lbs.)
²The number three bolt is then hand tightened
and torqued to 40 N´m ( 30 ft. lbs.)
²The number two bolt is also hand tightened and
torqued to 55 N´m ( 41 ft. lbs.)
(3) Remove the tape or plugs from all of the
opened refrigerant line fittings. Install the suction
and discharge line manifold to the compressor.
Tighten the fastener to 28 N´m (250 in. lbs.).(Refer to
24 - HEATING & AIR CONDITIONING/PLUMBING/
SUCTION LINE - INSTALLATION) (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING/A/C
DISCHARGE LINE - INSTALLATION)
(4) Install the serpentine drive belt(Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
INSTALLATION).
(5) Plug in the compressor clutch coil wire harness
connector.
(6) Connect the battery negative cable.
Fig. 3 COMPRESSOR REMOVE/INSTALL - DIESEL
ENGINE
1 - ENGINE
2 - BRACKET
3 - A/C COMPRESSOR
4 - BOLTS
Fig. 4 A/C COMPRESSOR - 3.7L ENGINE- (typical
4.7, 5.7 & 8.0L)
1 - COMPRESSOR BOLT #1
2 - COMPRESSOR BOLT #2
3 - COMPRESSOR BOLT #3
4 - A/C COMPRESSOR
5 - A/C COMPRESSOR CLUTCH AND PULLEY
6 - COMPRESSOR MOUNT
24 - 38 PLUMBINGDR
A/C COMPRESSOR (Continued)

(7) Evacuate the refrigerant system. (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - REFRIGERANT SYS-
TEM EVACUATE)
(8) Charge the refrigerant system. (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - REFRIGERANT SYS-
TEM CHARGE)
INSTALLATION - 5.9L DIESEL ENGINE
WARNING: REVIEW THE WARNINGS AND CAU-
TIONS IN THE FRONT OF THIS SECTION BEFORE
PERFORMING THE FOLLOWING OPERATION.
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - WARNING) (Refer to 24 - HEATING &
AIR CONDITIONING/PLUMBING - CAUTION)(Refer to
24 - HEATING & AIR CONDITIONING/PLUMBING -
CAUTION - REFRIGERANT HOSES/LINES/TUBES
PRECAUTIONS)
NOTE: If a replacement compressor is being
installed, be certain to check the refrigerant oil
level. (Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING/REFRIGERANT OIL - STANDARD PRO-
CEDURE) Use only refrigerant oil of the type
recommended for the compressor in the vehicle.
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING/REFRIGERANT OIL - DESCRIPTION)
(1) Install the compressor to the mounting bracket.
Tighten the four mounting bolts to 24 N´m (210 in.
lbs.).
(2) Remove the tape or plugs from all of the
opened refrigerant line fittings. Install the suction
and discharge line manifold to the compressor. (Refer
to 24 - HEATING & AIR CONDITIONING/PLUMB-
ING/A/C SUCTION AND DISCHARGE LINE -
INSTALLATION)
(3) Install the serpentine drive belt(Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
INSTALLATION).
(4) Plug in the compressor clutch coil wire harness
connector.
(5) Connect the battery negative cable.
(6) Evacuate the refrigerant system. (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - REFRIGERANT SYS-
TEM EVACUATE)
(7) Charge the refrigerant system. (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - REFRIGERANT SYS-
TEM CHARGE)
A/C CONDENSER
DESCRIPTION
The condenser is located in the air flow next to the
engine cooling radiator. The condenser is a heat
exchanger that allows the high-pressure refrigerant
gas being discharged by the compressor to give up its
heat to the air passing over the condenser fins.
OPERATION
When the refrigerant gas gives up its heat, it con-
denses. When the refrigerant leaves the condenser, it
has become a high-pressure liquid refrigerant. The
volume of air flowing over the condenser fins is crit-
ical to the proper cooling performance of the air con-
ditioning system. Therefore, it is important that
there are no objects placed in front of the radiator
grille openings in the front of the vehicle or foreign
material on the condenser fins that might obstruct
proper air flow. Also, any factory-installed air seals or
shrouds must be properly reinstalled following radia-
tor or condenser service.
The condenser cannot be repaired and, if faulty or
damaged, it must be replaced.
REMOVAL
REMOVAL - 3.7, 4.7 and 5.7L ENGINES
WARNING: REVIEW THE WARNINGS AND CAU-
TIONS IN THE FRONT OF THIS SECTION BEFORE
PERFORMING THE FOLLOWING OPERATION.
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - WARNING) (Refer to 24 - HEATING &
AIR CONDITIONING/PLUMBING - CAUTION)
(1) Disconnect and isolate the battery negative
cable.
(2) Recover the refrigerant from the refrigerant
system. (Refer to 24 - HEATING & AIR CONDI-
TIONING/PLUMBING - STANDARD PROCEDURE -
REFRIGERANT RECOVERY)
(3) Disconnect the discharge line refrigerant line
fitting at the condenser inlet. (Refer to 24 - HEAT-
ING & AIR CONDITIONING/PLUMBING - STAN-
DARD PROCEDURE - A/C LINE COUPLERS)
Install plugs in, or tape over all of the opened refrig-
erant line fittings.
(4) Disconnect the liquid line refrigerant line fit-
ting at the condenser outlet. (Refer to 24 - HEATING
& AIR CONDITIONING/PLUMBING - STANDARD
PROCEDURE - A/C LINE COUPLERS) Install plugs
in, or tape over all of the opened refrigerant line fit-
tings.
DRPLUMBING 24 - 39
A/C COMPRESSOR (Continued)

AIR CONDITIONING/PLUMBING - STANDARD
PROCEDURE - A/C LINE COUPLERS)
(4) Remove the tape or plugs from the refrigerant
line fittings on the condenser inlet and the discharge
line. Connect the discharge line to the condenser
inlet. (Refer to 24 - HEATING & AIR CONDITION-
ING/PLUMBING - STANDARD PROCEDURE - A/C
LINE COUPLERS)
(5) Connect the battery negative cable.
(6) Evacuate the refrigerant system. (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - REFRIGERANT SYS-
TEM EVACUATE)
(7) Charge the refrigerant system. (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - REFRIGERANT SYS-
TEM CHARGE)
NOTE: If the condenser is replaced, add 30 millili-
ters (1 fluid ounce) of refrigerant oil to the refriger-
ant system. Use only refrigerant oil of the type
recommended for the compressor in the vehicle.
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING/REFRIGERANT OIL - DESCRIPTION)
INSTALLATION - 5.9L DIESEL ENGINE
WARNING: REVIEW THE WARNINGS AND CAU-
TIONS IN THE FRONT OF THIS SECTION BEFORE
PERFORMING THE FOLLOWING OPERATION.
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - WARNING) (Refer to 24 - HEATING &
AIR CONDITIONING/PLUMBING - CAUTION)(Refer to
24 - HEATING & AIR CONDITIONING/PLUMBING -
CAUTION - REFRIGERANT HOSES/LINES/TUBES
PRECAUTIONS)
(1) On diesel engine models:
(a) Install the driver side condenser mounting
brackets over the two studs on the charge air
cooler.
(b) Install the two screws that secure the brack-
ets on the passenger side end of the condenser to
the charge air cooler. Tighten the mounting screws
to 10.5 N´m (95 in. lbs.).
(c) Install the two nuts that secure the driver
side end of the condenser to the studs on the
charge air cooler. Tighten the mounting nuts to
10.5 N´m (95 in. lbs.).
(2) Remove the plugs or tape from the refrigerant
line fittings on the liquid line and the condenser out-
let. Connect the liquid line to the condenser outlet.
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - STANDARD PROCEDURE - A/C LINE
COUPLERS)(3) Install a new gasket and the discharge line
block fitting over the stud on the condenser inlet.
Tighten the mounting nut to 20 N´m (180 in. lbs.).
(4) Check that all of the condenser and radiator
air seals are in their proper locations.
(5) Connect the battery negative cable.
(6) Evacuate the refrigerant system. (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - REFRIGERANT SYS-
TEM EVACUATE)
(7) Charge the refrigerant system. (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - REFRIGERANT SYS-
TEM CHARGE)
NOTE: If the condenser is replaced, add 30 millili-
ters (1 fluid ounce) of refrigerant oil to the refriger-
ant system. Use only refrigerant oil of the type
recommended for the compressor in the vehicle.
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING/REFRIGERANT OIL - DESCRIPTION)
INSTALLATION - 8.0L Engine
WARNING: REVIEW THE WARNINGS AND CAU-
TIONS IN THE FRONT OF THIS SECTION BEFORE
PERFORMING THE FOLLOWING OPERATION(Refer
to 24 - HEATING & AIR CONDITIONING/PLUMBING -
WARNING) AND (Refer to 24 - HEATING & AIR CON-
DITIONING/PLUMBING - CAUTION).
(1) If the condenser was removed from the shroud,
install it and tighten the mounting screws.
(2) Install the condenser and shroud in the vehicle.
Make sure the lower mounting flanges are positioned
correctly before installing the two mounting screws
to the radiator brace. Tighten the screws to spec.
(3) Remove and plugs or tape installed over the
condenser connections and the a/c lines.
(4) Install the lines to the condenser(Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING/A/C
DISCHARGE LINE - INSTALLATION) and (Refer to
24 - HEATING & AIR CONDITIONING/PLUMBING/
SUCTION LINE - INSTALLATION).
(5) Install the hood latch assembly(Refer to 23 -
BODY/HOOD/LATCH - INSTALLATION).
(6) Install the front bumper assembly(Refer to 13 -
FRAME & BUMPERS/BUMPERS/FRONT BUMPER
- INSTALLATION).
(7) Evacuate the a/c system(Refer to 24 - HEAT-
ING & AIR CONDITIONING/PLUMBING - STAN-
DARD PROCEDURE).
24 - 42 PLUMBINGDR
A/C CONDENSER (Continued)

NOTE: If the condenser is replaced, add 30 millili-
ters (1 fluid ounce) of refrigerant oil to the refriger-
ant system. Use only refrigerant oil of the type
recommended for the compressor in the vehicle(Re-
fer to 24 - HEATING & AIR CONDITIONING/PLUMB-
ING/REFRIGERANT OIL - DESCRIPTION).
(8) Charge the a/c system(Refer to 24 - HEATING
& AIR CONDITIONING/PLUMBING - STANDARD
PROCEDURE).
(9) Install the battery negative cable.
A/C CONDENSER FAN
REMOVAL - CONDENSER FAN (GAS ENGINE
ONLY - 3.7, 4.7 & 5.7L)
(1) Remove and isolate negative battery cable.
(2) Remove condenser assembly(Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING/A/C
CONDENSER - REMOVAL).
(3) Place condenser assembly on a flat work area
and remove screws holding fan assembly to con-
denser.
(4) Separate fan assembly from condenser noting
location of all seals for reinstallation.
INSTALLATION - CONDENSER FAN (GAS
ENGINE ONLY - 3.7, 4.7 & 5.7L)
(1) Position fan assembly on to the condenser.
(2) Check all fan shroud seals and replace as
required then install retainer screws to hold fan
assembly to condenser.
(3) Install condenser and fan assembly to vehi-
cle(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING/A/C CONDENSER - INSTALLATION).
(4) Install battery negative cable.
A/C DISCHARGE LINE
REMOVAL
REMOVAL
WARNING: REVIEW THE WARNINGS AND CAU-
TIONS IN THE FRONT OF THIS SECTION BEFORE
PERFORMING THE FOLLOWING OPERATION.
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - WARNING) (Refer to 24 - HEATING &
AIR CONDITIONING/PLUMBING - CAUTION)
(1) Disconnect and isolate the battery negative
cable.
(2) Recover the refrigerant from the refrigerant
system. (Refer to 24 - HEATING & AIR CONDI-TIONING/PLUMBING - STANDARD PROCEDURE -
REFRIGERANT RECOVERY)
(3) Unplug the wire harness connector from the
high pressure transducer.
(4) Disconnect the discharge line refrigerant line
fitting from the condenser inlet tube (Fig. 9). (Refer
to 24 - HEATING & AIR CONDITIONING/PLUMB-
ING - STANDARD PROCEDURE - A/C LINE COU-
PLERS) Install plugs in, or tape over all of the
opened refrigerant line fittings.
(5) Disconnect the connection that secures the suc-
tion line fitting to the accumulator outlet. Install
plugs in, or tape over all of the opened refrigerant
line fittings.
(6) Remove the screw that secures the suction and
discharge line manifold to the compressor. Install
plugs in, or tape over all of the opened refrigerant
line fittings.
(7) Remove the suction and discharge line assem-
bly from the vehicle.REMOVAL - 5.9L DIESEL ENGINE
WARNING: REVIEW THE WARNINGS AND CAU-
TIONS IN THE FRONT OF THIS SECTION BEFORE
PERFORMING THE FOLLOWING OPERATION.
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - WARNING) (Refer to 24 - HEATING &
AIR CONDITIONING/PLUMBING - CAUTION)
(1) Disconnect and isolate the battery negative
cable.
Fig. 9 A/C Discharge Line
1 - Discharge Line Retainer Nut
2 - Front Upper Cross Brace
3 - Condensor Module Port
4 - Suction and Discharge Line Retainer Screw
5 - Suction Line
6 - A/C Compressor
7 - High Pressure Transducer Connector
8 - Discharge Line
DRPLUMBING 24 - 43
A/C CONDENSER (Continued)

INSTALLATION
WARNING: REVIEW THE WARNINGS AND CAU-
TIONS IN THE FRONT OF THIS SECTION BEFORE
PERFORMING THE FOLLOWING OPERATION.
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - WARNING) (Refer to 24 - HEATING &
AIR CONDITIONING/PLUMBING - CAUTION)(Refer to
24 - HEATING & AIR CONDITIONING/PLUMBING -
CAUTION - REFRIGERANT HOSES/LINES/TUBES
PRECAUTIONS)
(1) Install the accumulator to the bulkhead but do
not tighten yet.
(2) Remove the tape or plugs from the refrigerant
line fittings on the accumulator inlet and the evapo-
rator outlet. Connect the accumulator inlet refriger-
ant line coupler to the evaporator outlet. (Refer to 24
- HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - A/C LINE COUPLERS)
(3) Remove the tape or plugs from the refrigerant
line fittings on the suction line and the accumulator
outlet. Connect the suction line refrigerant line cou-
pler to the accumulator outlet. (Refer to 24 - HEAT-
ING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - A/C LINE COUPLERS)
(4) Tighten the accumulator fasteners to 4.5 N´m
(40 in. lbs.).
(5) Connect the battery negative cable.
(6) Evacuate the refrigerant system. (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - REFRIGERANT SYS-
TEM EVACUATE)
(7) Charge the refrigerant system. (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - REFRIGERANT SYS-
TEM CHARGE)
NOTE: If the accumulator is replaced, add 60 milli-
liters (2 fluid ounces) of refrigerant oil to the refrig-
erant system. Use only refrigerant oil of the type
recommended for the compressor in the vehicle.
HEATER CORE
DESCRIPTION
The heater core is located in the HVAC housing,
under the instrument panel. It is a heat exchanger
made of rows of tubes and fins.
The heater core is not repairable and if damaged it
must be replaced.
OPERATION
Engine coolant is circulated through heater hoses
to the heater core at all times. As the coolant flowsthrough the heater core, heat removed from the
engine is transferred to the heater core fins and
tubes. Air directed through the heater core picks up
the heat from the heater core fins. The blend door
allows control of the heater output air temperature
by controlling how much of the air flowing through
the HVAC housing is directed through the heater
core. The blower motor speed controls the volume of
air flowing through the HVAC housing.
The heater core cannot be repaired and, if faulty or
damaged, it must be replaced.
REMOVAL
NOTE: Disassembly of the HVAC housing is not
required to remove heater core.
(1) Remove the HVAC housing from the vehicle.
(Refer to 24 - HEATING & AIR CONDITIONING/
DISTRIBUTION/HVAC HOUSING - REMOVAL)
(2) Remove the screws and retainers that secure
the heater core to the HVAC housing.
(3) Lift the heater core out of the heater-A/C hous-
ing.
(4) Inspect all seals and repair or replace as
required.
INSTALLATION
(1) Place the heater core into the HVAC housing.
(2) Snap the retainers for the heater core to the
housing. Install and tighten the screws that secure
the heater core to the HVAC housing (if equipped).
Tighten the screws to 2.2 N´m (20 in. lbs.).
(3) Reinstall the HVAC housing in the vehicle.
(Refer to 24 - HEATING & AIR CONDITIONING/
DISTRIBUTION/HVAC HOUSING - INSTALLA-
TION)
REFRIGERANT
DESCRIPTION
The refrigerant used in this air conditioning sys-
tem is a HydroFluoroCarbon (HFC), type R-134a.
Unlike R-12, which is a ChloroFluoroCarbon (CFC),
R-134a refrigerant does not contain ozone-depleting
chlorine. R-134a refrigerant is a non-toxic, non-flam-
mable, clear, and colorless liquefied gas.
Even though R-134a does not contain chlorine, it
must be reclaimed and recycled just like CFC-type
refrigerants. This is because R-134a is a greenhouse
gas and can contribute to global warming.
OPERATION
R-134a refrigerant is not compatible with R-12
refrigerant in an air conditioning system. Even a
24 - 50 PLUMBINGDR
ACCUMULATOR (Continued)

verter. The PCM calculates the A/F mixture from the
output of the O2S. A low voltage indicates high oxy-
gen 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 a
totally 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 will be illu-
minated.
DESCRIPTION - TRIP DEFINITION
The term ªTripº has different meanings depending
on what the circumstances are. If the MIL (Malfunc-
tion Indicator Lamp) is OFF, a Trip is defined as
when the Oxygen Sensor Monitor and the Catalyst
Monitor have been completed in the same drive cycle.
When any Emission DTC is set, the MIL on the
dash is turned ON. When the MIL is ON, it takes 3
good trips to turn the MIL OFF. In this case, it
depends on what type of DTC is set to know what a
ªTripº is.
For the Fuel Monitor or Mis-Fire Monitor (contin-
uous monitor), the vehicle must be operated in the
ªSimilar Condition Windowº for a specified amount of
time to be considered a Good Trip.
If a Non-Contiuous OBDII Monitor fails twice in a
row and turns ON the MIL, re-running that monitor
which previously failed, on the next start-up and
passing the monitor, is considered to be a Good Trip.
These will include the following:
²Oxygen Sensor²Catalyst Monitor
²Purge Flow Monitor
²Leak Detection Pump Monitor (if equipped)
²EGR Monitor (if equipped)
²Oxygen Sensor Heater Monitor
If any other Emission DTC is set (not an OBDII
Monitor), a Good Trip is considered to be when the
Oxygen Sensor Monitor and Catalyst Monitor have
been completed; or 2 Minutes of engine run time if
the Oxygen Sensor Monitor or Catalyst Monitor have
been stopped from running.
It can take up to 2 Failures in a row to turn on the
MIL. After the MIL is ON, it takes 3 Good Trips to
turn the MIL OFF. After the MIL is OFF, the PCM
will self-erase the DTC after 40 Warm-up cycles. A
Warm-up cycle is counted when the ECT (Engine
Coolant Temperature Sensor) has crossed 160ÉF and
has risen by at least 40ÉF since the engine has been
started.
DESCRIPTION - COMPONENT MONITORS
There are several components that will affect vehi-
cle emissions if they malfunction. If one of these com-
ponents malfunctions the Malfunction Indicator
Lamp (MIL) will illuminate.
Some of the component monitors are checking for
proper operation of the part. Electrically operated
components now have input (rationality) and output
(functionality) checks. Previously, a component like
the Throttle Position sensor (TPS) was checked by
the PCM for an open or shorted circuit. If one of
these conditions occurred, a DTC was set. Now there
is a check to ensure that the component is working.
This is done by watching for a TPS indication of a
greater or lesser throttle opening than MAP and
engine rpm indicate. In the case of the TPS, if engine
vacuum is high and engine rpm is 1600 or greater,
and the TPS indicates a large throttle opening, a
DTC will be set. The same applies to low vacuum if
the TPS indicates a small throttle opening.
All open/short circuit checks, or any component
that has an associated limp-in, will set a fault after 1
trip with the malfunction present. Components with-
out an associated limp-in will take two trips to illu-
minate the MIL.
OPERATION
OPERATION
The Powertrain Control Module (PCM) monitors
many different circuits in the fuel injection, ignition,
emission and engine systems. If the PCM senses a
problem with a monitored circuit often enough to
indicate an actual problem, it stores a Diagnostic
Trouble Code (DTC) in the PCM's memory. If the
25 - 4 EMISSIONS CONTROLDR
EMISSIONS CONTROL (Continued)