TESTS
1. Verify the battery state of charge (Refer to 8 - ELECTRICAL/BATTERY SYSTEM/BATTERY - DIAGNOSIS AND
TESTING).
2. Connect an ammeter (0 to 10 ampere scale selected) in series with the clutch coil feed terminal. Connect a
voltmeter (0 to 20 volt scale selected) to measure voltage across the battery and the clutch coil.
3. With the A/C-heater control in the A/C mode and the blower motor at low speed, start the engine and allow it to
run at a normal idle speed.
4. The A/C compressor clutch should engage immediately, and the clutch coil supply voltage should be within two
volts of the battery voltage. If the coil supply voltage is OK, go to Step 5. If the coil supply voltage is not within
two volts of battery voltage, test the clutch coil feed circuit for excessive voltage drop and repair as necessary.
5. For the acceptable A/C clutch coil current draw specifications refer to24 - HEATING & AIR CONDITIONING -
SPECIFICATIONS. Specifications apply for a work area temperature of 21° C(70° F). If voltage is more than
12.5 volts, add electrical loads by turning on electrical accessories until voltage reads below 12.5 volts.
STANDARD PROCEDURE
A/C CLUTCH PLATE INSPECTION
NOTE: The A/C clutch can be serviced inthe vehicle. The refrigerant systemcan remain fully-charged dur-
ing compressor clutch, pulley and bearing assembly, or coil replacement.
Examine the friction surfaces of the pulley and the
clutch plate (2) for wear. The pulley and clutch plate
should be replaced if there is excessive wear or scor-
ing.
If the friction surfaces are oily, inspect the shaft and
nose area of the A/C compressor (1) for refrigerant oil.
If refrigerant oil is found, the compressor shaft seal is
leaking and the A/C compressor must be replaced.
Check the pulley bearing for roughness or excessive
leakage of grease. Replace the pulley and bearing
assembly, if required.
A/C CLUTCH BREAK-IN
After a new A/C compressor clutch hasbeen installed, cycle the compressorclutch approximately 20 times (5 sec-
onds on, then 5 seconds off). During this procedure, set the A/C-heater controls to the A/C Recirculation Mode, the
blower motor in the highest speed position, and the engine speed at 1500 to 2000 rpm. This procedure (burnishing)
will seat the opposing friction surfaces and provide a higher compressor clutch torque capability.
SENSOR-EVAPORATOR TEMPERATURE
DESCRIPTION
The evaporator temperature sensor is a two-wire tem-
perature sensing element located at the coldest point
on the face of the A/C evaporator. The probe (1) for
evaporator temperature sensor is attached to the
evaporator coil fins. The wire lead (2) for evaporator
temperature sensor is routed through an opening at
the back of the HVAC housing and the connector (3)
is attached to the HVAC wire harness.
OPERATION
The evaporator temperature sensor monitors the surface temperature of A/C evaporator and supplies an input signal
to the A/C-heater control. The A/C-heater control uses the evaporator temperature sensor input signal to optimize
A/C system performance and to protect the A/C system from evaporator freezing. The evaporator temperature sen-
sor will change its internal resistance in response to the temperatures itmonitors and is connected to the A/C-heater
control through sensor ground circuit and a 5-volt reference signal circuit. As the temperature of the A/C evaporator
decreases, the internal resistance of the evaporator temperature sensordecreases.
The A/C-heater control uses the monitored voltage reading as an indication of evaporator temperature. The A/C-
heater control is programmed to respond to this input by requesting the powertrain control module (PCM) or the
engine control module (ECM) (depending on engine application) to cycle the A/C compressor clutch as necessary to
optimize A/C system performance and to protect the A/C system from evaporatorfreezing(Referto24-HEATING
& AIR CONDITIONING/CONTROLS/COIL-A/C COMPRESSOR CLUTCH - OPERATION formore information).
The evaporator temperature sensor is diagnosed using a scan tool (Refer to24 - HEATING & AIR CONDITIONING
- DIAGNOSIS AND TESTING and to 24 - HVAC Electrical Diagnostics for more information).
The evaporator temperature sensor cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.
PLUMBING
DESCRIPTION
The A/C refrigerant lines and hoses are used to carry the refrigerant between the various A/C system components.
The refrigerant lines and hoses for the R-134a system on this vehicle consist of a barrier-hose design with a nylon
tube sandwiched between rubber layers. The nylon tube helps to contain theR-134a refrigerant, which has a
smaller molecular structure than R-12 refrigerant. The ends of the refrigerant lines are made from lightweight alu-
minum or steel, and commonly use braze-less fittings.
Any kinks or sharp bends in the refrigerant lines and hoses will reduce the capacity of the entire A/C system and
can reduce the flow of refrigerant in the system. The radius of all bends in the flexible hose refrigerant lines should
be at least ten times the diameter of the hose and the refrigerant lines should be routed so they are at least 80
millimeters (3 inches) away from the exhaust manifold(s) and exhaust pipe(s).
OPERATION
High pressures are produced in the refrigerant system when the A/C compressor is operating. 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 oncea year to make sure they are in good con-
dition and properly routed.
The refrigerant lines and hoses are coupled to other A/C system componentswith block-type fittings. An O-ring seal,
or a flat steel gasket with an integral O-ring (dual plane seal), is used to mate the refrigerant line fittings with A/C
system components to ensure the integrity of the refrigerant system.
The refrigerant lines and hoses cannot be repaired and, if faulty or damaged, they must be replaced.
WARNING
WARNING: The A/C system contains refrigerant under high pressure. Repairs should only be performed by
qualified service personnel. Severe personal injury or death may result from improper service procedures.
WARNING: Avoid breathing the refrigerant and refrigerant oil vapor or mist. Exposure may irritate the eyes,
nose, and/or throat. Wear eye protection when servicing the A/C refrigerant system. Serious eye injury can
result from direct contact with the refrigerant. If eye contact occurs, seek medical attention immediately.
WARNING: Do not expose the refrigerant to open flame. Poisonous gas is createdwhenrefrigerantis
burned. An electronic leak detector is recommended. Severe personal injury or death may result from
improper service procedures.
WARNING: If accidental system discharge occurs, ventilate the work area before resuming service. Large
amounts of refrigerant released in a closed work area will displace the oxygen and cause suffocation and
death.
WARNING: The evaporation rate of R-134a refrigerant at average temperature and altitude is extremely high.
As a result, anything that comes in contact with the refrigerant will freeze. Always protect the skin or del-
icate objects from direct contact with the refrigerant.
WARNING: The R-134a service equipment or the vehicle refrigerant system should not be pressure tested or
leak tested with compressed air. Some mixtures of air and R-134a have been shown to be combustible at
elevated pressures. These mixtures are potentially dangerous, and may result in fire or explosion causing
property damage, personal injury or death.
RECOVERY/RECYCLING/EVACUATION/CHARGING HOSE– The center manifold hose (Yellow, or White, with
Black stripe) (3) is used to recover, evacuate, and charge the refrigerantsystem. When the low or high pressure
valves on the manifold gauge set are opened, the refrigerant in the system will escape through this hose.
HIGH PRESSURE GAUGE HOSE– The high pressure hose (Red with Black stripe) (4) attaches to the high side
service port. This service port is located on the A/C discharge line. On this model, an A/C pressure transducer is
installed on the high side service port. A/C high-side pressures can be read using a scan tool. Refer to 9 - Engine
Electrical Diagnostics for more information.
LOW PRESSURE GAUGE HOSE– The low pressure hose (Blue with Black stripe) (5) attaches to the low side
service port. This service port is located either on the top of the A/C accumulator or on the A/C suction line near the
accumulator, depending on engine application.
REFRIGERANT SYSTEM RECOVERY
WARNING: Refer to the applicable warnings and cautions for this system before performing the following
operation (Refer to 24 - HEATING & AIR CONDITIONING/PLUMBING - WARNINGS) and (Refer to 24 - HEAT-
ING & AIR CONDITIONING/PLUMBING - CAUTIONS). Failure to follow the warnings and cautions could result
in possible personal injury or death.
An R-134a refrigerant recovery/recycling/charging sta-
tion (1) that meets SAE standard J2210 must be used
to recover the refrigerant from the R-134a refrigerant
system. Refer to the operating instructions supplied by
the equipment manufacturer for the proper care and
use of this equipment.
REFRIGERANT SYSTEM EVACUATE
NOTE: Special effort must be used to prevent moisture from entering the A/Csystem oil. Moisture in the oil
is very difficult to remove and will cause a reliability problem with the compressor.
If an A/C compressor designed to use R-134a refrigerant is left open to the atmosphere for an extended period of
time. It is recommended that the refrigerant oil be drained and replaced with new oil or a new A/C compressor be
used. This will eliminate the possibility of contaminating the refrigerant system.
If the refrigerant system has been open to the atmosphere, it must be evacuated before the system can be filled.
Moisture and air mixed with the refrigerant will raise the compressor headpressure above acceptable operating
levels. This will reduce the performance of the A/C system and damage the A/C compressor. Moisture will boil at
near room temperature when exposed to vacuum. To evacuate the refrigerantsystem:
NOTE: When connecting the service equipment coupling to the line fitting,verify that the valve of the cou-
pling is fully closed. This will reduce the amount of effort required to make the connection.
1. Recover the refrigerant system (Refer to 24 - HEATING & AIR CONDITIONING/PLUMBING - STANDARD PRO-
CEDURE - REFRIGERANT SYSTEM RECOVERY).
2. Connect a suitable charging station, refrigerant recovery machine or amanifold gauge set with vacuum pump
and refrigerant recovery equipment (Refer to 24 - HEATING & AIR CONDITIONING/PLUMBING - STANDARD
PROCEDURE - REFRIGERANT SYSTEM SERVICE EQUIPMENT).
3. Open the suction and discharge valves and start the vacuum pump. The vacuum pump should run a minimum of
45minutespriortochargetoeliminateall moisture in system. When the suction gauge reads to the lowest
COMPRESSOR-A/C
DESCRIPTION
A/C COMPRESSOR
NOTE: Denso 10S17 compressor shown. Visteon
HS-18 compressor similar.
The A/C system on models equipped with the 3.7L,
4.7L, 5.7L and 8.3L engines use a Denso 10S17
reciprocating swash plate-type compressor (1). This
A/C compressor has a fixed displacement of 170 cubic
centimeters (10.3 cubic inches).
The A/C system on models equipped with the 5.9L
diesel engine use a Visteon HS-18 A/C compressor.
This A/C compressor is a 10 cylinder reciprocating
swash plate-type compressor with a fixed displace-
ment of 180 cubic centimeters (10.9 cubic inches).
Both A/C compressors have the suction and discharge
ports (2) located on the compressor cylinder head (3)
at the rear of the compressor and have a label identi-
fying the use of R-134a refrigerant.
HIGH PRESSURE RELIEF VALVE
A high pressure relief valve is located on the A/C compressor. This mechanical valve is designed to vent refrigerant
from the A/C system to protect against damage to the A/C compressor and other A/C system components, caused
by condenser air flow restriction or an overcharge of refrigerant.
OPERATION
A/C COMPRESSOR
The A/C compressor is driven by the engine through an electric clutch, drive pulley and belt arrangement. The A/C
compressor is lubricated by refrigerant oil that is circulated throughout the refrigerant system with the refrigerant.
The A/C compressor draws in low-pressure refrigerant vapor from the A/C evaporator through its suction port. It then
compresses the refrigerant into a high-pressure, high-temperature refrigerant vapor, which is then pumped to the
A/C condenser through the compressor discharge port.
The A/C compressor cannot be repaired and, if faulty or damaged, it must be replaced. The compressor clutch,
pulley and bearing assembly, and clutch field coil are available for service. If an internal failure of the A/C compres-
sor has occurred, the A/C accumulator must also be replaced.
HIGH PRESSURE RELIEF VALVE
The high pressure relief valve vents refrigerant from the A/C system when adischarge pressure of 3445 to 4135
kPa (500 to 600 psi) or above is reached. The high pressure relief valve closes with a minimum discharge pressure
of 2756 kPa (400 psi) is reached.
The high pressure relief valve vents only enough refrigerant to reduce theA/C system pressure, and then re-seats
itself. The majority of the refrigerant is conserved in the A/C system. If the high pressure relief valve vents refrig-
erant, it does not mean the valve is faulty.
The high pressure relief valve is factory-calibrated and cannot be adjusted or repaired, and must not be removed or
otherwise disturbed. The valve is only serviced as a part of the A/C compressor.
DIAGNOSIS AND TESTING
A/C COMPRESSOR
When investigating an A/C system related noise, you must first know the conditions under which the noise occurs.
These conditions include: weather, vehicle speed, transmission in gear or neutral, engine speed, engine tempera-
ture, and any other special conditions. Noises that develop during A/C operation can often be misleading. For exam-
ple: What sounds like a failed front engine 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 dependingupon drive belt tension, drive belts can
develop noises that are mistaken for an A/C compressor noise. Improper drive belt tension can cause a misleading
noise when the compressor clutch is engaged, which may not occur when the compressor clutch is disengaged.
Check the accessory 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. Turn the A/C compressor
On and Off several times to clearly identify the compressor noise. Listen to the A/C compressor while the clutch
is engaged and disengaged. Probe the A/C compressor with an engine stethoscope or a long screwdriver with
the handle held to your ear to better localize the source of the noise.
2. Loosen all of the compressor mounting hardware and retighten. Check thecompressor clutch retainer. Be certain
that the clutch field coil is mounted securely to the A/C compressor, and that the clutch plate and pulley are
properly aligned and have the correct air gap (Refer to 24 - HEATING & AIR CONDITIONING/CONTROLS/
CLUTCH-A/C COMPRESSOR - INSTALLATION).
3. To duplicate high-ambient temperature conditions (high head pressure), restrict the air flow through the A/C con-
denser. Install a manifold gauge set or a scan tool to be certain that the discharge 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 and hoses for kinks or sharp bendsthat will restrict refrigerant flow, which
can cause noises (Refer to 24 - HEATING & AIR CONDITIONING/PLUMBING - DESCRIPTION - REFRIGER-
ANT LINES).
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 - HEATING & AIR CONDITIONING/PLUMBING - STANDARD PROCEDURE -
REFRIGERANT SYSTEM RECOVERY), (Refer to 24 - HEATING & AIR CONDITIONING/PLUMBING - STAN-
DARD PROCEDURE - REFRIGERANT SYSTEM EVACUATE) and (Refer to 24 - HEATING & AIR CONDITION-
ING/PLUMBING - STANDARD PROCEDURE - REFRIGERANT SYSTEM CHARGE). If the high pressure relief
valve still does not seat properly, replace the A/C compressor (Refer to 24- HEATING & AIR CONDITIONING/
PLUMBING/COMPRESSOR-A/C - REMOVAL).
6. If the noise is from liquid refrigerant slugging in the A/C suction line,replace the A/C accumulator (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING/ACCUMULATOR-A/C - REMOVAL) and check the refrigerant oil
level and the refrigerant system charge (Refer to 24 - HEATING & AIR CONDITIONING/PLUMBING/REFRIG-
ERANT OIL - STANDARD PROCEDURE - REFRIGERANT OIL LEVEL) (Refer to 24 - HEATING & AIR CON-
DITIONING/PLUMBING- STANDARD PROCEDURE - REFRIGERANT SYSTEM CHARGE).
7. If a slugging condition still exists after replacing the A/C accumulator, then replace the A/C compressor (Refer to
24 - HEATING & AIR CONDITIONING/PLUMBING/COMPRESSOR-A/C - REMOVAL) and repeat Step 1.
REMOVAL
3.7L/4.7L ENGINES
WARNING: Refer to the applicable warnings and cautions for this system before performing the following
operation (Refer to 24 - HEATING & AIR CONDITIONING/PLUMBING - WARNINGS) and (Refer to 24 - HEAT-
ING & AIR CONDITIONING/PLUMBING - CAUTIONS). Failure to follow the warnings and cautions could result
in possible personal injury or death.
NOTE: The A/C compressor may be removed and repositioned without disconnecting the refrigerant lines or
discharging the refrigerant system. Discharging is not necessary if servicing the compressor clutch, clutch
coil, engine, engine cylinder head or the generator.
EVAPORATOR-A/C
DESCRIPTION
The A/C evaporator (1) for the heating-A/C system is
located within the HVAC housing, behind the instru-
ment panel. The A/C evaporator and its insulator (2)
are positioned in the HVAC housing so that all air
entering the housing must pass over the evaporator
fins before it is distributed through the heating-A/C
system ducts and outlets. However, air passing over
the evaporator fins will only be conditioned when the
A/C compressor is engaged and circulating refrigerant
through the A/C evaporator.
The A/C evaporator can be serviced by removing and
disassembling the HVAC housing assembly.
OPERATION
Refrigerant enters the A/C evaporator through the A/C orifice tube as a low-temperature, low-pressure mixture of
liquid and gas. As air flows over the fins of the A/C evaporator, the humidity in the air condenses on the fins, and
the heat from the air is absorbed by the refrigerant. Heat absorption causes the refrigerant to boil and vaporize. The
refrigerant becomes a low-pressure gas when it leaves the A/C evaporator.
The A/C evaporator cannot be repaired and, if faulty or damaged, it must be replaced.
REMOVAL
1. RemovetheHVAChousingandplaceitonawork-
bench (Refer to 24 - HEATING & AIR CONDITION-
ING/DISTRIBUTION/HOUSING-HVAC -
REMOVAL).
2. Disassemble the HVAC housing to access the A/C
evaporator (Refer to 24 - HEATING & AIR CONDI-
TIONING/DISTRIBUTION/HOUSING-HVAC - DIS-
ASSEMBLY).
3. Remove the probe of the evaporator temperature
sensor (1) from the fins of the A/C evaporator (2)
and position the wire lead (3) out of the way.
NOTE: If the foam insulator around the A/C evap-
orator is deformed or damaged, the insulator must
be replaced.
4. Carefully lift the A/C evaporator and the foam insu-
lator out of the upper half of the HVAC housing (4).
NOTE: If the foam seal around the evaporator tap-
ping block is deformed or damaged, the seal must be replaced.
5. If required, remove the foam seal from the inlet and outlet tubes of the A/Cevaporator.
INSTALLATION
NOTE: If the A/C evaporator is being replaced, add 60 milliliters (2 fluid ounces) of refrigerant oil to the
refrigerant system. Use only refrigerant oil of the type recommended for the A/C compressor in the vehicle.
NOTE: Make sure that the foam insulator is prop-
erly positioned in the HVAC housing.
1. Carefully install the A/C evaporator (2) and its foam
insulator into the upper half of the HVAC housing
(4).
2. Install the probe of the evaporator temperature
sensor (1) between the fins of the A/C evaporator.
3. Route the wire lead (3) of the evaporator tempera-
ture sensor into the opening located on the upper
half of the HVAC housing.
4. Assemble the HVAC housing (Refer to 24 - HEAT-
ING & AIR CONDITIONING/DISTRIBUTION/
HOUSING-HVAC - ASSEMBLY).
5. Install the HVAC housing (Refer to 24 - HEATING
& AIR CONDITIONING/DISTRIBUTION/HOUSING-
HVAC - INSTALLATION).