1998 DODGE RAM 1500 Engine

The A/C pressure transducer cannot be adjusted or
repaired and, if faulty or damaged, it must be
replaced.
OPERATION
The A/C pressure transducer monitors the pres-
sures in the high side of the refrigerant system
through its connection to a fitting on the discharge
line. The transducer will change its internal resis-
tance in response to the pressures it monitors. The
Powertrain Control Module (PCM) or the Engine
Control Module (ECM) depending on engine applica-
tion, provides a five volt reference signal and a sen-
sor ground to the transducer, then monitors the
output voltage of the transducer on a sensor return
circuit to determine refrigerant pressure. The PCM/
ECM is programmed to respond to this and other
sensor inputs by controlling the operation of the air
conditioning compressor clutch and the radiator cool-
ing fan to help optimize air conditioning system per-
formance and to protect the system components from
damage. The A/C pressure transducer input to the
PCM/ECM will also prevent the air conditioning com-
pressor clutch from engaging when ambient temper-
atures are below about 10É C (50É F) due to the
pressure/temperature relationship of the refrigerant.
The Schrader-type valve in the discharge line fitting
permits the A/C pressure transducer to be removed
or installed without disturbing the refrigerant in the
system. The A/C pressure transducer is diagnosed
using a DRBIIItscan tool. Refer to the appropriate
diagnostic information.
DIAGNOSIS AND TESTING - A/C PRESSURE
TRANSDUCER
The A/C pressure transducer is tested using a
DRBIIItscan tool. Refer to the appropriate diagnos-
tic information. Before testing the A/C pressure
transducer, be certain that the transducer wire har-
ness connection is clean of corrosion and properly
connected. For the air conditioning system to operate,
an A/C pressure transducer voltage reading between
0.451 and 4.519 volts is required. Voltages outside
this range indicate a low or high refrigerant system
pressure condition to the Powertrain Control Module
(PCM) or Engine Control Module (ECM) depending
on engine application. The PCM/ECM is programmed
to respond to a low or high refrigerant system pres-
sure by suppressing operation of the compressor.
Refer to the A/C Pressure Transducer Voltage chart
for the possible conditions indicated by the trans-
ducer voltage reading.
A/C PRESSURE TRANSDUCER VOLTAGE
CHART
Voltage Possible Indication
0.0 1. No sensor supply voltage from
PCM/ECM.
2. Shorted sensor circuit.
3. Faulty transducer.
0.150 TO 0.450 1. Ambient temperature below
10É C (50É F).
2. Low refrigerant system
pressure.
0.451 TO 4.519 1. Normal refrigerant system
pressure.
4.520 TO 4.850 1. High refrigerant system
pressure.
5.0 1. Open sensor circuit.
2. Faulty transducer.
REMOVAL
NOTE: Note: It is not necessary to discharge the
refrigerant system to replace the A/C pressure
transducer.
(1) Disconnect and isolate the battery negative
cable.
(2) Disconnect the wire harness connector from the
A/C pressure transducer.
(3) Remove the A/C pressure transducer from the
fitting on the discharge line (Fig. 15).
(4) Remove the O-ring seal from the A/C pressure
transducer fitting and discard.
INSTALLATION
NOTE: Replace the O-ring seal before installing the
A/C pressure transducer.
(1) Lubricate a new rubber O-ring seal with clean
refrigerant oil and install it on the A/C pressure
transducer 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 recom-
mended for the A/C compressor in the vehicle.
(2) Install and tighten the A/C pressure transducer
onto the discharge line fitting. The transducer should
be hand-tightened securely onto the discharge line
fitting.
(3) Connect the wire harness connector to the A/C
pressure transducer.
24 - 16 CONTROLSDR
A/C PRESSURE TRANSDUCER (Continued)

INSTALLATION
(1) Install the floor distribution duct onto the bot-
tom of the HVAC housing.
(2) Install the five screws that secure the floor dis-
tribution duct to the HVAC housing. Tighten the
screws to 2.2 N´m (20 in. lbs.).
(3) Install the HVAC housing (Refer to 24 - HEAT-
ING & AIR CONDITIONING/DISTRIBUTION/HVAC
HOUSING - INSTALLATION).
HVAC HOUSING
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.
NOTE: The HVAC housing must be removed from
the vehicle and the two halves of the housing sep-
arated for service access of the heater core, evap-
orator coil, defrost door, blend door(s) and the
recirculation door.
(1) Disconnect and isolate the battery negative
cable.
(2) Drain the engine cooling system (Refer to 7 -
COOLING - STANDARD PROCEDURE).
(3) Recover the refrigerant from the refrigerant
system (Refer to 24 - HEATING & AIR CONDITION-
ING/PLUMBING - STANDARD PROCEDURE -
REFRIGERANT RECOVERY).
(4) Disconnect the liquid refrigerant line fitting
from the evaporator inlet tube (Refer to 24 - HEAT-
ING & AIR CONDITIONING/PLUMBING/REFRIG-
ERANT LINE COUPLER - REMOVAL). Discard the
O-ring seal and install plugs in, or tape over the
opened liquid refrigerant line fitting and evaporator
inlet tube.
(5) Remove the accumulator (Refer to 24 - HEAT-
ING & AIR CONDITIONING/PLUMBING/ACCU-
MULATOR - REMOVAL). Discard the O-ring seals
and install plugs in, or tape over the opened refrig-
erant line fittings and evaporator outlet tube.(6) Disconnect the heater hoses from the heater
core tubes. Install plugs in, or tape over the opened
heater core tubes.
(7) Remove the powertrain control module (PCM)
from the engine compartment to gain access to the
HVAC housing retaining nuts (Refer to 8 - ELECTRI-
CAL/ELECTRONIC CONTROL MODULES/POWER-
TRAIN CONTROL MODULE - REMOVAL).
(8) Remove the two nuts from the HVAC housing
mounting studs in the engine compartment.
(9) Remove the instrument panel from the vehicle
(Refer to 23 - BODY/INSTRUMENT PANEL -
REMOVAL).
(10) Remove the bolt that secures the HVAC hous-
ing to the floor bracket located in the center of the
vehicle (Fig. 9).
(11) Remove the two nuts from the HVAC housing
mounting studs in the passenger compartment.
(12) Remove the HVAC housing from inside the
vehicle. Take care not to allow any remaining coolant
to drain onto the vehicles interior.
Fig. 9 HVAC Housing - Dual Zone Shown, Single
Zone Typical
1 - NUT
2 - PASSENGER BLEND DOOR ACTUATOR
3 - NUT
4 - INLET BAFFLE
5 - RECIRCULATION DOOR ACTUATOR
6 - RECIRCULATION DOOR
7 - DRIVER SIDE BLEND DOOR ACTUATOR
8 - HVAC HOUSING
9 - BOLT
10 - DEFROSTER DOOR ACTUATOR
11 - MODE DOOR ACTUATOR
24 - 34 DISTRIBUTIONDR
FLOOR DISTRIBUTION DUCT (Continued)

ING/CONTROLS/BLOWER MOTOR RESISTOR
BLOCK - INSTALLATION).
(5) If removed, install the blower motor (Refer to
24 - HEATING & AIR CONDITIONING/DISTRIBU-
TION/BLOWER MOTOR - INSTALLATION).
(6) Install the HVAC wire harness. Make sure the
wires are routed through all wiring retainers.
(7) Connect the wire harness to the blower motor,
blower motor resistor block, evaporator temperature
sensor and each actuator.
(8) Install the HVAC housing (Refer to 24 - HEAT-
ING & AIR CONDITIONING/DISTRIBUTION/HVAC
HOUSING - INSTALLATION).
INSTALLATION
WARNING: IF THE VEHICLE IS EQUIPPED WITH AIR
CONDITIONING, REVIEW THE WARNINGS AND
CAUTIONS IN PLUMBING BEFORE PERFORMING
THE FOLLOWING OPERATION. (Refer to 24 - HEAT-
ING & AIR CONDITIONING/PLUMBING - WARNING)
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - CAUTION) (Refer to 24 - HEATING &
AIR CONDITIONING/PLUMBING - CAUTION -
REFRIGERANT HOSES/LINES/TUBES PRECAU-
TIONS)
(1) Position the HVAC housing into the vehicle. Be
certain that the evaporator condensate drain tube
and the housing mounting studs are inserted into
their correct locations.
(2) Install the two nuts that secure the HVAC
housing to the mounting studs in the passenger com-
partment. Tighten the nuts to 6.2 N´m (55 in. lbs.).
(3) Install the bolt that secures the HVAC housing
to the floor bracket in the passenger compartment.
Tighten the bolt to 6.2 N´m (55 in. lbs.).
(4) Install the instrument panel (Refer to 23 -
BODY/INSTRUMENT PANEL - INSTALLATION).
(5) Install the two nuts that secure the HVAC
housing to the mounting studs in the engine com-
partment. Tighten the nuts to 6.2 N´m (55 in. lbs.).
(6) Install the powertrain control module (PCM)
(Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/POWERTRAIN CONTROL MOD-
ULE - INSTALLATION).
(7) Unplug or remove the tape from the heater
core tubes and connect the heater hoses to the heater
core tubes.
(8) Unplug or remove the tape from the opened
refrigerant line fittings and the evaporator outlet
tube and install the accumulator (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING/AC-
CUMULATOR - INSTALLATION).
(9) Unplug or remove the tape from the liquid line
and the evaporator inlet tube fittings. Connect the
liquid line coupler to the evaporator inlet tube (Referto 24 - HEATING & AIR CONDITIONING/PLUMB-
ING - STANDARD PROCEDURE - A/C LINE COU-
PLERS).
(10) Evacuate the refrigerant system (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - REFRIGERANT SYS-
TEM EVACUATE).
(11) Charge the refrigerant system (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - REFRIGERANT SYS-
TEM CHARGE).
(12) Fill the engine cooling system (Refer to 7 -
COOLING/ENGINE - STANDARD PROCEDURE).
(13) Connect the battery negative cable.
(14) Start the engine and check for proper opera-
tion of the heating and air conditioning systems.
INSTRUMENT PANEL
DEMISTER DUCTS
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 ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
(1) Remove the defroster ducts (Refer to 24 -
HEATING & AIR CONDITIONING/DISTRIBUTION/
DEFROSTER DUCTS - REMOVAL).
(2) Remove the two screws that secure the center
distribution duct to the instrument panel support.
(3) Remove the center distribution duct from
instrument panel support, panel ducts and demister
ducts.
(4) Remove the right side panel duct adapter (Fig.
11).
(5) Remove the right side intermediate demister
duct.
(6) Remove the left side intermediate demister
duct.
(7) Remove the left side panel duct adapter.
(8) Remove the instrument panel cover (Refer to
23 - BODY/INSTRUMENT PANEL/INSTRUMENT
PANEL TOP COVER - REMOVAL).
24 - 36 DISTRIBUTIONDR
HVAC HOUSING (Continued)

PLUMBING
TABLE OF CONTENTS
page page
PLUMBING
DESCRIPTION - REFRIGERANT LINE.......42
OPERATION- REFRIGERANT LINES........42
WARNING
ENGINE COOLING SYSTEM.............42
A/C SYSTEM.........................43
CAUTION
A/C SYSTEM.........................43
DIAGNOSIS AND TESTING - REFRIGERANT
SYSTEM LEAKS......................44
STANDARD PROCEDURE
STANDARD PROCEDURE - HANDLING
TUBING AND FITTINGS.................45
STANDARD PROCEDURE - DIODE
REPLACEMENT.......................45
STANDARD PROCEDURE - REFRIGERANT
SYSTEM SERVICE EQUIPMENT..........46
STANDARD PROCEDURE - REFRIGERANT
RECOVERY..........................47
STANDARD PROCEDURE - REFRIGERANT
SYSTEM EVACUATE...................47
STANDARD PROCEDURE - REFRIGERANT
SYSTEM CHARGE.....................47
A/C COMPRESSOR
DESCRIPTION
DESCRIPTION - A/C COMPRESSOR.......48
DESCRIPTION - HIGH PRESSURE RELIEF
VALVE..............................48
OPERATION
OPERATION - A/C COMPRESSOR........48
OPERATION - HIGH PRESSURE RELIEF
VALVE..............................48
DIAGNOSIS AND TESTING - A/C
COMPRESSOR.......................49
REMOVAL.............................49
INSTALLATION.........................51
A/C CONDENSER
DESCRIPTION.........................52
OPERATION...........................52
REMOVAL
REMOVAL - 3.7, 4.7 AND 5.7L ENGINES....52
REMOVAL - 5.9L DIESEL ENGINE.........53
INSTALLATION
INSTALLATION - 3.7, 4.7 AND 5.7L ENGINES . 53
INSTALLATION - 5.9L DIESEL ENGINE.....54
A/C CONDENSER FAN
REMOVAL - 3.7, 4.7 and 5.7L ENGINES......55
INSTALLATION - 3.7, 4.7 and 5.7L ENGINES . . . 55A/C DISCHARGE LINE
DESCRIPTION.........................56
REMOVAL
REMOVAL - 5.9L DIESEL ENGINE.........56
REMOVAL - 3.7L/4.7L AND 5.7L HEMI
ENGINE.............................57
INSTALLATION
INSTALLATION - 5.9L DIESEL ENGINE.....58
INSTALLATION - 3.7L/4.7L AND 5.7L HEMI
ENGINE.............................59
A/C EVAPORATOR
DESCRIPTION.........................59
OPERATION...........................59
REMOVAL.............................60
INSTALLATION.........................60
A/C ORIFICE TUBE
DESCRIPTION.........................60
OPERATION...........................60
DIAGNOSIS AND TESTING - A/C ORIFICE
TUBE...............................61
ACCUMULATOR
DESCRIPTION.........................61
OPERATION...........................61
REMOVAL.............................61
INSTALLATION.........................62
HEATER CORE
DESCRIPTION.........................63
OPERATION...........................63
REMOVAL.............................63
INSTALLATION.........................63
HEATER INLET HOSE
REMOVAL.............................64
INSTALLATION.........................64
HEATER RETURN HOSE
REMOVAL.............................64
INSTALLATION.........................65
LIQUID LINE
DESCRIPTION.........................65
REMOVAL.............................65
INSTALLATION.........................66
REFRIGERANT
DESCRIPTION.........................67
OPERATION...........................67
REFRIGERANT LINE COUPLER
DESCRIPTION.........................67
OPERATION...........................67
REMOVAL.............................68
INSTALLATION.........................68
DRPLUMBING 24 - 41

REFRIGERANT OIL
DESCRIPTION.........................68
OPERATION...........................69
STANDARD PROCEDURE - REFRIGERANT
OIL LEVEL...........................69
SERVICE PORT VALVE CORE
DESCRIPTION.........................70
REMOVAL - SERVICE PORT VALVE CORES . . 70
INSTALLATION.........................70
SUCTION LINE
DESCRIPTION.........................70REMOVAL
REMOVAL - 5.9L DIESEL ENGINE.........70
REMOVAL - 3.7L/4.7L AND 5.7L HEMI
ENGINE.............................71
INSTALLATION
INSTALLATION - 5.9L DIESEL ENGINE.....72
INSTALLATION - 3.7L/4.7L AND 5.7L HEMI
ENGINE.............................73
PLUMBING
DESCRIPTION - REFRIGERANT LINE
The refrigerant lines and hoses are used to carry
the refrigerant between the various air conditioning
system components. A barrier hose design with a
nylon tube, which is sandwiched between rubber lay-
ers, is used for the R-134a air conditioning system on
this vehicle. This nylon tube helps to further contain
the R-134a refrigerant, which has a smaller molecu-
lar structure than R-12 refrigerant. The ends of the
refrigerant hoses are made from lightweight alumi-
num or steel, and commonly use braze-less fittings.
Any kinks or sharp bends in the refrigerant plumb-
ing will reduce the capacity of the entire air condi-
tioning system. Kinks and sharp bends reduce the
flow of refrigerant in the system. 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.
In addition, the flexible hose refrigerant lines should
be routed so they are at least 80 millimeters (3
inches) from an exhaust manifold.
OPERATION- REFRIGERANT LINES
High pressures are produced in the refrigerant sys-
tem when the air conditioning compressor is operat-
ing. Extreme care must be exercised to make sure
that each of the refrigerant system connections is
pressure-tight and leak free. It is a good practice to
inspect all flexible hose refrigerant lines at least once
a year to make sure they are in good condition and
properly routed.
The refrigerant lines and hoses are coupled with
other components of the HVAC system with either
O-rings or dual plane seals.
The refrigerant lines and hoses cannot be repaired
and, if faulty or damaged, they must be replaced.
WARNING
ENGINE COOLING SYSTEM
WARNING: THE ENGINE COOLING SYSTEM IS
DESIGNED TO DEVELOP INTERNAL PRESSURES
OF 97 TO 123 KILOPASCALS (14 TO 18 POUNDS
PER SQUARE INCH). DO NOT REMOVE OR
LOOSEN THE COOLANT PRESSURE CAP, CYLIN-
DER BLOCK DRAIN PLUGS, RADIATOR DRAIN,
RADIATOR HOSES, HEATER HOSES, OR HOSE
CLAMPS WHILE THE ENGINE COOLING SYSTEM IS
HOT AND UNDER PRESSURE. FAILURE TO
OBSERVE THIS WARNING CAN RESULT IN SERI-
OUS BURNS FROM THE HEATED ENGINE COOL-
ANT. ALLOW THE VEHICLE TO COOL FOR A
MINIMUM OF 15 MINUTES BEFORE OPENING THE
COOLING SYSTEM FOR SERVICE.
24 - 42 PLUMBINGDR

DIAGNOSIS AND TESTING - REFRIGERANT
SYSTEM LEAKS
WARNING: R-134a SERVICE EQUIPMENT OR VEHI-
CLE A/C SYSTEM SHOULD NOT BE PRESSURE
TESTED OR LEAK TESTED WITH COMPRESSED
AIR. MIXTURE OF AIR and R-134a CAN BE COM-
BUSTIBLE AT ELEVATED PRESSURES. THESE MIX-
TURES ARE POTENTIALLY DANGEROUS AND MAY
RESULT IN FIRE OR EXPLOSION CAUSING INJURY
OR PROPERTY DAMAGE.
AVOID BREATHING A/C REFRIGERANT AND LUBRI-
CANT VAPOR OR MIST. EXPOSURE MAY IRRITATE
EYES, NOSE AND THROAT. USE ONLY APPROVED
SERVICE EQUIPMENT MEETING SAE REQUIRE-
MENTS TO DISCHARGE R-134a SYSTEM. IF ACCI-
DENTAL SYSTEM DISCHARGE OCCURS,
VENTILATE WORK AREA BEFORE RESUMING SER-
VICE.
NOTE: The refrigerant system does come from the
factory with a yellow tracer dye already installed to
aid in detection of leaks.
If the A/C system is not cooling properly, determine
if the refrigerant system is fully charged with
R-134a. This is accomplished by performing a system
Charge Level-Check or Fill. If while performing this
test A/C liquid line pressure is less than 345 kPa (50
psi) proceed to System Empty procedure. If liquid
line pressure is greater than 345 kPa (50 psi) proceed
to System Low procedure. If the refrigerant system is
empty or low in refrigerant charge, a leak at any line
fitting or component seal is likely. A review of the fit-
tings, lines and components for oily residue is an
indication of the leak location. To detect a leak in the
refrigerant system, perform one of the following pro-
cedures as indicated by the symptoms.
SYSTEM EMPTY
(1) Evacuate the refrigerant system to the lowest
degree of vacuum possible (approx. 28 in Hg.). Deter-
mine if the system holds a vacuum for 15 minutes. If
vacuum is held, a leak is probably not present. If sys-
tem will not maintain vacuum level, proceed with
this procedure.(2) Prepare a 0.284 Kg. (10 oz.) refrigerant charge
to be injected into the system.
(3) Connect and dispense 0.284 Kg. (10 oz.) of
refrigerant into the evacuated refrigerant system.
(4) Proceed to Step 2 of System Low procedure.
SYSTEM LOW
(1) Determine if there is any (R-134a) refrigerant
in the system.
(2) Position the vehicle in a wind free work area.
This will aid in detecting small leaks.
(3) Bring the refrigerant system up to operating
temperature and pressure. This is done by allowing
the engine to run for five minutes with the system
set to the following:
²Transmission in Park or Neutral with parking
brake set
²Engine idling at 700 rpm
²A/C controls set in 100 percent outside air
²Blower switch in the high A/C position
²A/C in the ON position
²Open all windows
CAUTION: A leak detector designed for R-12 refrig-
erant (only) will not detect leaks in a R-134a refrig-
erant system.
(4) Shut off the vehicle and wait 2 to 7 minutes.
Then use an Electronic Leak Detector that is
designed to detect R-134a type refrigerant and search
for leaks. Fittings, lines, or components that appear
to be oily usually indicates a refrigerant leak. To
inspect the evaporator core for leaks, insert the leak
detector probe into the drain tube opening or a heat
duct. A R-134a dye is available to aid in leak detec-
tion, use only DaimlerChrysler approved refrigerant
dye.
24 - 44 PLUMBINGDR
PLUMBING (Continued)

After the system has been tested for leaks and
evacuated, a refrigerant (R-134a) charge can be
injected into the system.
NOTE: When connecting the service equipment
coupling to the line fitting, verify that the valve of
the coupling is fully closed. This will reduce the
amount of effort required to make the connection.
(1) If using a separate vacuum pump close all
valves before disconnecting pump. Connect manifold
gauge set to the A/C service ports.
NOTE: Always refer to the underhood HVAC Speci-
fication label for the refrigerant fill level of the vehi-
cle being serviced.
(2) Measure refrigerant (refer to capacities). Refer
to the instructions provided with the equipment
being used.
(3) Verify engine is shut off. Open the suction and
discharge valves. Open the charge valve to allow the
refrigerant to flow into the system. When the trans-
fer of refrigerant has stopped, close the suction and
discharge valve.
(4) If all of the charge did not transfer from the
dispensing device, put vehicle controls into the fol-
lowing mode:
²Automatic transmission in park or manual
transmission in neutral
²Engine at idle
²A/C mode control set to outside air
²A/C mode control set to panel mode
²A/C temperature control set to full cool
²Blower motor control set on highest speed
²Vehicle windows closed
If the A/C compressor does not engage, test the
compressor clutch control circuit and correct any fail-
ure (Refer to 8 - ELECTRICAL/WIRING DIAGRAM
INFORMATION - DIAGNOSIS AND TESTING).
(5) Open the suction valve to allow the remaining
refrigerant to transfer to the system.
WARNING: TAKE CARE NOT TO OPEN THE DIS-
CHARGE (HIGH-PRESSURE) VALVE AT THIS TIME.
(6) Close all valves and test the A/C system perfor-
mance.
(7) Disconnect the charging station or manifold
gauge set. Install the service port caps.
REFRIGERANT CHARGE CAPACITY
The R-134a refrigerant system charge capacity for
this vehicle can be found on the underhood HVAC
specfication tag.
A/C COMPRESSOR
DESCRIPTION
DESCRIPTION - A/C COMPRESSOR
The A/C system on models equipped with the 5.9L
engine use a Sanden SD-7 reciprocating swash plate-
type compressor. This compressor has a fixed dis-
placement of 165 cubic centimeter (10.068 cubic
inches) and has both the suction and discharge ports
located on the cylinder head.
The A/C system on models equipped with the 3.7L,
4.7L and 5.7L engines use a Denso 10S17 reciprocat-
ing swash plate-type compressor. This compressor
has a fixed displacement of 170 cubic centimeter and
has both the suction and discharge ports located on
the cylinder head.
A label identifying the use of R-134a refrigerant is
located on both A/C compressors.
DESCRIPTION - HIGH PRESSURE RELIEF
VALVE
A high pressure relief valve is located on the com-
pressor cylinder head, which is on the rear of the
compressor. This mechanical valve is designed to
vent refrigerant from the system to protect against
damage to the compressor and other system compo-
nents, caused by condenser air flow restriction or an
overcharge of refrigerant.
OPERATION
OPERATION - A/C COMPRESSOR
The A/C compressor is driven by the engine
through an electric clutch, drive pulley and belt
arrangement. The compressor is lubricated by refrig-
erant oil that is circulated throughout the refrigerant
system with the refrigerant.
The compressor draws in low-pressure refrigerant
vapor from the evaporator through its suction port. It
then compresses the refrigerant into a high-pressure,
high-temperature refrigerant vapor, which is then
pumped to the condenser through the compressor dis-
charge port.
The compressor cannot be repaired. If faulty or
damaged, the entire compressor assembly must be
replaced. The compressor clutch, pulley and clutch
coil are available for service.
OPERATION - HIGH PRESSURE RELIEF VALVE
The high pressure relief valve vents the system
when a discharge pressure of 3445 to 4135 kPa (500
to 600 psi) or above is reached. The valve closes
24 - 48 PLUMBINGDR
PLUMBING (Continued)

when a minimum discharge pressure of 2756 kPa
(400 psi) is reached.
The high pressure relief valve vents only enough
refrigerant to reduce the system pressure, and then
re-seats itself. The majority of the refrigerant is con-
served in the system. If the valve vents refrigerant, it
does not mean that the valve is faulty.
The high pressure relief valve is a factory-cali-
brated unit. The valve cannot be adjusted or
repaired, and must not be removed or otherwise dis-
turbed. The valve is only serviced as a part of the
compressor assembly.
DIAGNOSIS AND TESTING - A/C COMPRESSOR
When investigating an air conditioning related
noise, you must first know the conditions under
which the noise occurs. These conditions include:
weather, vehicle speed, transmission in gear or neu-
tral, engine speed, engine temperature, and any
other special conditions. Noises that develop during
air conditioning operation can often be misleading.
For example: What sounds like a failed front bearing
or connecting rod, may be caused by loose bolts, nuts,
mounting brackets, or a loose compressor clutch
assembly.
Drive belts are speed sensitive. At different engine
speeds and depending upon belt tension, belts can
develop noises that are mistaken for a compressor
noise. Improper belt tension can cause a misleading
noise when the compressor clutch is engaged, which
may not occur when the compressor clutch is disen-
gaged. Check the serpentine drive belt condition and
tension as described in Cooling before beginning this
procedure.
(1) Select a quiet area for testing. Duplicate the
complaint conditions as much as possible. Switch the
compressor on and off several times to clearly iden-
tify the compressor noise. Listen to the compressor
while the clutch is engaged and disengaged. Probe
the compressor with an engine stethoscope or a long
screwdriver with the handle held to your ear to bet-
ter localize the source of the noise.
(2) Loosen all of the compressor mounting hard-
ware and retighten. Tighten the compressor clutch
mounting nut. Be certain that the clutch coil is
mounted securely to the compressor, and that the
clutch plate and rotor are properly aligned and have
the correct air gap (Refer to 24 - HEATING & AIR
CONDITIONING/CONTROLS/A/C COMPRESSOR
CLUTCH - INSTALLATION).
(3) To duplicate a high-ambient temperature condi-
tion (high head pressure), restrict the air flow
through the condenser. Install a manifold gauge set
or a DRBIIItscan tool to be certain that the dis-
charge pressure does not exceed 2760 kPa (400 psi).(4) Check the refrigerant system plumbing for
incorrect routing, rubbing or interference, which can
cause unusual noises. Also check the refrigerant lines
for kinks or sharp bends that will restrict refrigerant
flow, which can cause noises (Refer to 24 - HEATING
& AIR CONDITIONING/PLUMBING - STANDARD
PROCEDURE).
(5) If the noise is from opening and closing of the
high pressure relief valve, recover, evacuate and
recharge the refrigerant system (Refer to 24 - HEAT-
ING & AIR CONDITIONING/PLUMBING - STAN-
DARD PROCEDURE), (Refer to 24 - HEATING &
AIR CONDITIONING/PLUMBING - STANDARD
PROCEDURE - REFRIGERANT SYSTEM EVACU-
ATE) and (Refer to 24 - HEATING & AIR CONDI-
TIONING/PLUMBING - STANDARD PROCEDURE -
REFRIGERANT SYSTEM CHARGE). If the high
pressure relief valve still does not seat properly,
replace the compressor (Refer to 24 - HEATING &
AIR CONDITIONING/PLUMBING/A/C COMPRES-
SOR - REMOVAL).
(6) If the noise is from liquid slugging on the suc-
tion line, replace the accumulator (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING/AC-
CUMULATOR - REMOVAL) and check the refriger-
ant oil level and the refrigerant system charge (Refer
to 24 - HEATING & AIR CONDITIONING/PLUMB-
ING/REFRIGERANT OIL - STANDARD PROCE-
DURE) (Refer to 24 - HEATING & AIR
CONDITIONING/PLUMBING/ACCUMULATOR -
REMOVAL). If after replacing the accumulator the
slugging condition still exists then replace the com-
pressor.(Refer to 24 - HEATING & AIR CONDITION-
ING/PLUMBING/A/C COMPRESSOR - REMOVAL).
(7) If the liquid slugging condition continues fol-
lowing accumulator replacement, replace the com-
pressor and repeat Step 1.
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) and (Refer to 24 - HEATING & AIR CON-
DITIONING/PLUMBING - CAUTION).
NOTE: The A/C compressor may be removed and
repositioned without disconnecting the refrigerant
lines or discharging the refrigerant system. Dis-
charging is not necessary if servicing the compres-
sor clutch, clutch coil, engine, engine cylinder head
or the generator.
(1) Recover the refrigerant from the refrigerant
system (Refer to 24 - HEATING & AIR CONDITION-
DRPLUMBING 24 - 49
A/C COMPRESSOR (Continued)