1993 CHEVROLET DYNASTY service

VACUUM CONTROL SYSTEM DIAGNOSIS
GENERAL INFORMATION
Use an adjustable Vacuum Test Gauge (C-3707)
and a suitable vacuum pump to test heater A/C con-
trol vacuum. With a finger placed over the end of
test hose (Fig. 1), calibrate vacuum control valve on
the test gauge to obtain -27 kPa (8 in. Hg.). Release
and block the end of the test hose several times to
verify vacuum setting.
VACUUM TESTING THE ONE-WAY CHECK VALVE
(1) In the engine compartment, disconnect the
Heater-A/C vacuum supply (black) hose. This hose
passes through an opening in the dash panel used for
the air conditioning expansion valve. (2) Remove the vacuum check valve. This valve is
located on the (black) vacuum supply hose at the
brake power booster. (3) Connect test vacuum supply hose to the heater
side of the valve. In this direction the gauge should
return to calibrated setting. If valve leaks vacuum in
this direction, valve replacement is necessary. (4) Connect test vacuum supply hose to the engine
vacuum side of the valve. Vacuum should flow
through valve.
VACUUM TESTING THE HEATER-A/C CONTROLS
(1) Connect the test vacuum prod to the vehicles
(black) vacuum supply hose. Position vacuum test
gauge so it can be viewed from the passenger com-
partment. (2) Position the heater A/C control mode selector to
DEFROST, FLOOR, BI-LEVEL, PANEL, and RE-
CIRC (with A/C). Pause after each selection. The test
gauge should return to the calibrated setting of -27
kPa (8 in. Hg.) after each selection is made. If the
gauge cannot achieve the calibrated setting, a vac-
uum circuit or component has a leak.
LOCATING VACUUM LEAKS
To locate a vacuum leak, disconnect 7-way vacuum
connector behind the instrument panel at the heater
A/C control. For removal and installation of heater
A/C control panel, refer to the Switch and Panel
Component Service section of Group 8E, Instrument
Panel. Connect the calibrated vacuum hose prod (Fig.
4) to each port in the vacuum harness connector (Fig.
2). The brown, bi-level, vacuum circuit has a metal
fiber restrictive device located in the line. More reac-
tion time is required for the test gauge to return to
calibrated setting. After each connection is made, the
test gauge should return to calibrated setting. If all
circuits function properly, replace control mode vac-
uum switch. If not, determine the color of the vac-
uum circuit that is leaking. To determine vacuum
line colors, refer to the Vacuum Circuits-Heater or
Heater A/C Control chart in this section. Disconnect
the vacuum actuator at the other end of the circuit.
(Instrument panel removal may be necessary to gain
access to some components). Block the end of the dis-
connected vacuum line. The test gauge should return
to calibrated setting. If not, that circuit has a leak
and must be repaired or replaced. If test gauge re-
turns to calibrated setting, the vacuum actuator
must be replaced.
Fig. 1 Adjust Vacuum Test Bleed Valve
Fig. 2 Vacuum Circuit Test
24 - 4 HEATING AND AIR CONDITIONING Ä

HEATER AND A/C PERFORMANCE TESTS
HEATER OUTPUT TEST
PRE-DIAGNOSTIC PREPARATIONS
Review Safety Precautions and Warnings before
performing the following procedures. Check the radiator coolant level, drive belt tension,
and engine vacuum line connections. Also check ra-
diator air flow and radiator fan operation. Start en-
gine and allow to warm up to normal operating
temperature.
WARNING: DO NOT REMOVE RADIATOR CAP
WHEN ENGINE IS HOT, PERSONAL INJURY CAN
RESULT.
If vehicle has been run recently, wait 15 minutes
before removing cap. Place a rag over the cap and
turn it to the first safety stop. Allow pressure to es-
cape through the overflow tube. When the system
stabilizes, remove the cap completely.
MAXIMUM HEATER OUTPUT: TEST AND ACTION
Engine coolant is provided to the heater system by
two 16 mm (5/8 inch inside diameter) heater hoses.
With engine idling at normal running temperature,
set the control to maximum heat, floor, and high
blower setting. Using a test thermometer, check the
air temperature coming from the floor outlets, refer
to Temperature Reference chart.
If the floor outlet air temperature is low, refer to
Group 7, Cooling System for coolant temperature
specifications. Both heater hoses should be HOT to
the touch. The coolant return hose should be slightly
cooler than the supply hose. If coolant return hose is
much cooler than the supply hose, locate and repair
engine coolant flow obstruction in heater system.
POSSIBLE LOCATIONS OR CAUSE OF OBSTRUCTED
COOLANT FLOW
(a) Pinched or kinked heater hoses.
(b) Improper heater hose routing. (c) Plugged heater hoses or supply and return
ports at cooling system connections, refer to Group
7, Cooling System. (d) Plugged heater core.
If proper coolant flow through heater system is ver-
ified and outlet air temperature is still low, a me-
chanical problem may exist.
POSSIBLE LOCATION OR CAUSE OF INSUFFICIENT HEAT
(a) Obstructed cowl air intake.
(b) Obstructed heater system outlets.
(c) Blend-air door not functioning properly.
TEMPERATURE CONTROL If temperature cannot be adjusted with the TEMP
lever on the control panel, or TEMP lever is difficult
to move, the following could require service: (a) Blend-air door binding.
(b) Control cables miss-routed, pinched, kinked,
or disconnected. (c) Improper engine coolant temperature.A/C PERFORMANCE TEST
The air conditioning system is designed to remove
heat and humidity from the air entering the passen-
ger compartment. The evaporator, located in the
heater A/C unit behind the instrument panel, is
cooled to temperatures near the freezing point. As
warm damp air passes over the fins in the evapora-
tor, moisture in the air condenses to water, dehumid-
ifying the air. Condensation on the evaporator fins
reduces the evaporators ability to absorb heat. Dur-
ing periods of high heat and humidity an A/C system
will be less effective than during periods of high heat
and low humidity. With the instrument control set to
RECIRC, only air from the passenger compartment
passes through the evaporator. As the passenger
compartment air dehumidifies, A/C performance lev-
els rise.
PERFORMANCE TEST PROCEDURE
Review Safety Precautions and Warnings before
proceeding with this procedure. Air temperature in
test room and on vehicle must be 70ÉF (21ÉC) mini-
mum for this test. (1) Connect a tachometer and manifold gauge set.
(2) Set control to A/C, RECIRC, PANEL, or MAX
A/C, temperature lever on full cool and blower on
high. (3) Start engine and hold at 1000 rpm with A/C
clutch engaged. (4) Engine should be warmed up with doors and
windows closed.
TEMPERATURE REFERENCE CHART
24 - 6 HEATING AND AIR CONDITIONING Ä

REFRIGERANT SERVICE PROCEDURES INDEX
page page
Adding Partial Refrigerant Charge ............ 10
Charging Refrigerant SystemÐEmpty System . . . 11
Discharging Refrigerant System .............. 11
Evacuating Refrigerant System .............. 11
Manifold Gauge Set Connections ............. 9 Oil Level
............................... 12
R-12 Refrigerant Equipment ................. 8
Refrigerant Recycling ...................... 9
Sight Glass Refrigerant Level Inspection ........ 8
Testing for Refrigerant Leaks ............... 10
SIGHT GLASS REFRIGERANT LEVEL INSPECTION
The filter-drier is equipped with a sight glass (Fig.
1) that is used as a refrigerant level indicator only.
This sight glass is not to be used for A/C perfor-
mance testing. To check the refrigerant level re-
move the vehicle jack. Then clean the sight glass,
start and warm up engine, and hold rpm slightly
above idle (1100 rpm). Place the air conditioning con-
trol on A/C, RECIRC and high blower. The work
area should be at least 21ÉC (70ÉF). If a Fixed Dis-
placement type compressor does not engage, the re-
frigerant level is probably too low for the Low
Pressure Cut-Off switch to detect. Or, with a Vari-
able Displacement compressor, for the Differential
Pressure Cut-off to detect. If compressor clutch does
not engage, test the refrigerant system for leaks. If
compressor clutch engages, allow approximately one
minute for refrigerant to stabilize. View refrigerant
through sight glass. The suction line should be cold
to the touch and the sight glass should be clear.
If foam or bubbles are visible in sight glass, the re- frigerant level is probably low. Occasional foam or
bubbles are normal when the work area temperature
is above 43ÉC (110ÉF) or below 21ÉC (70ÉF). If suction
line is cold and occasional bubbles are visible in the
sight glass, block the condenser air flow. This will in-
crease the compressor discharge pressure. Do not al-
low engine to over heat. Bubbles should dissipate.
If not, the refrigerant level is low.
CAUTION: Do not allow engine to over heat while
blocking the condenser air flow.
WARNING: R-12 REFRIGERANT IS DETRIMENTAL
TO THE ENVIRONMENT WHEN RELEASED TO THE
ATMOSPHERE. DO NOT ADD R-12 REFRIGERANT
TO A SYSTEM THAT HAS A KNOWN LEAK.
The refrigerant system will not be low on (R-12)
unless there is a leak. Find and repair the leak be-
fore charging.
R-12 REFRIGERANT EQUIPMENT
WARNING: EYE PROTECTION MUST BE USED
WHEN SERVICING AN AIR CONDITIONING REFRIG-
ERANT SYSTEM. TURN OFF (ROTATE CLOCKWISE)
ALL VALVES ON THE EQUIPMENT BEING USED
BEFORE PROCEEDING WITH THIS OPERATION.
PERSONNEL INJURY CAN RESULT.
When servicing an air conditioning system, an A/C
charging station is recommended (Fig. 2). An (R-12)
refrigerant recovery/recycling device (Fig. 3) should
also be used. This device should meet SAE standards.
Contact an automotive service equipment supplier
for refrigerant recycling/recovering equipment. Refer
to the operating instructions provided with the
equipment for proper operation. A manifold gauge set (Fig. 4) must also be used in
conjunction with the charging and/or recovery/recy-
cling device. The service hoses on the gauge set be-
ing used should have manual (turn wheel) or
automatic back flow valves at the service port con-
nector ends. This will prevent refrigerant from being
release into the atmosphere.
Fig. 1 Filter Drier and Sight Glass
24 - 8 HEATING AND AIR CONDITIONING Ä

REFRIGERANT RECYCLING
(R-12) refrigerant is a chlorofluorocarbon (CFC)
that can contribute to the depletion of the ozone
layer in the upper atmosphere. To help protect the
ozone layer, an R-12 recycling device must be used.
Contact an automotive service equipment supplier
for refrigerant recycling equipment. Refer to the op-
erating instructions provided with the recycling
equipment for proper operation.
MANIFOLD GAUGE SET CONNECTIONS
GENERAL INFORMATION
The high pressure (discharge) (RED) hose should
be attached to the 1/4 in. discharge service port. This
port is located on the discharge line between the A/C
compressor and the condenser, or on the high pres-
sure (liquid) line. The low pressure (suction) (BLUE) hose should be
attached to the 3/8 in. suction service port. This port
is located on the air conditioning compressor, or the
suction line between the expansion valve and the
compressor.
SUCTION (LOW PRESSURE) GAUGE CONNECTION
(1) Remove the service port cap from 3/8 in. suc-
tion service port. (2) Check all valves on the equipment being used
to verify they are closed. (3) Inspect the hose gasket in the service port con-
nector at the end of the (BLUE) hose. If the gasket is
flawed, replace it. (4) Thread the hose connector onto the service
port. Quickly secure hose connector to the service
port to avoid loosing refrigerant. To disconnect suction gauge (BLUE) hose:(a) Wrap the end of hose with a shop towel.
(b) Loosen the hose connector.
(c) Push and hold the end of hose toward the ser-
vice port to keep the gasket in contact with service
port. (d) Quickly rotate the connector counterclock-
wise. When the hose connector is completely
Fig. 2 Refrigerant Charging StationÐTypical
Fig. 3 Refrigerant Recovery/Recycling StationÐTypical
Fig. 4 Manifold Gauge SetÐTypical
Ä HEATING AND AIR CONDITIONING 24 - 9

backed off, immediately point the end of hose toward
floor, as possibly trapped refrigerant in the hose will
be released.(e) Install service port cap.
DISCHARGE (HIGH PRESSURE) GAUGE CONNECTION (1) Remove the service port cap from the 1/4 in.
service port. (2) Check all valves on the equipment being used to
verify they are closed. (3) Inspect the hose gasket in the service port con-
nector at the end of the (RED) hose. If the gasket is
flawed, replace it. (4) Use a suitable (3/8 in. male to 1/4 in. female)
adapter (Fig. 5), threaded securely into the end of the
(RED) hose connector.
(5) Thread the 1/4 in. hose adapter connector onto
the service port. Quickly secure adapter connector to
service port to avoid loosing refrigerant. To disconnect the discharge gauge (RED) hose:(a) Wrap the end of hose with a shop towel.
(b) Loosen the hose connector.
(c) Push and hold the end of hose toward the
service port to keep the gasket in contact with service
port. (d) Quickly rotate the connector counterclockwise.
When the hose connector is completely backed off,
immediately point the end of hose toward floor, as
possibly trapped refrigerant in the hose will be
released. (e) Install service port cap.
EVACUATION/RECOVERY/RECYCLING/CHARGING LINE CON-
NECTION
The center manifold (YELLOW) or (WHITE) hose is
used to recycle, recover, evacuate, and charge the
refrigerant system. When the discharge or suction
valves on the manifold gauge set are opened, the
refrigerant in the system will escape through this hose. This hose should be attached to a R-12
Recovery/Recycling device. Refer to the
Recovery/Recycling devices operators manual
for procedures. For disconnection of this hose, refer to Disconnect-
ing the Discharge Gauge (RED) hose in the preced-
ing paragraphs.
TESTING FOR REFRIGERANT LEAKS
If the A/C system is not cooling properly, deter-
mine if the refrigerant system is fully charged with
R-12. Follow the procedures in the Performance Test
Procedures section of this Group. If the refrigerant
system is empty or low in refrigerant charge, a leak
at any line fitting or component seal is likely. To de-
tect a leak in the refrigerant system, perform one of
the following procedures as indicated by the symp-
toms.
EMPTY REFRIGERANT SYSTEM LEAK TEST
CAUTION: Review Safety Precautions and Warnings
in General Information section of this Group.
(1) Evacuate the refrigerant system to the lowest
degree of vacuum possible. (2) Prepare a 10 oz. refrigerant (R-12) charge to be
injected into the system. Refer to Charging Refriger-
ant System for instructions. (3) Connect and dispense 10 ozs. of refrigerant into
the evacuated refrigerant system. (4) Proceed to step two of Low Refrigerant Level
Leak Test.
LOW REFRIGERANT LEVEL LEAK TEST
Caution: Review Safety Precautions and Warnings
in the General Information section of this group.
(1) Using the refrigerant level sight glass, deter-
mine if there is any (R-12) 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. (4) With the engine not running, use an Electronic
Leak Detector (or equivalent) and search for leaks.
Fittings, lines, or components that appear to be oily
usually will indicate a refrigerant leak. To inspect
the evaporator core for leaks, it is possible to insert
the leak detector probe into the recirculating air door
opening (Fig. 6).
ADDING PARTIAL REFRIGERANT CHARGE
After all leaks have been corrected and it was not
necessary to empty the refrigerant system, a partial
refrigerant charge can be added.
CAUTION:Review all Safety Precautions and Warn-
ings before attempting to add refrigerant to the sys-
tem. Do not add refrigerant to a system that is
known to have a leak.
Fig. 5 Discharge Hose Adapter
24 - 10 HEATING AND AIR CONDITIONING Ä

(1) Attach manifold gauge set.
(2) Open the windows of the passenger compart-
ment and set the air conditioning controls to A/C,
RECIRC, and Low blower speed. (3) Start the engine and allow it to warm up to
normal running temperature. (4) If the air conditioning compressor does not en-
gage, disconnect the low pressure cut-off switch.
Place a jumper wire across the terminals in the con-
nector boot. If the compressor still does not engage, a
problem exists in the compressor clutch feed circuit. (6) Hold the engine speed at 1400 rpm.
(7) Following the instructions provided with the
charging equipment being used. Charge through the
suction side of the system. Use enough refrigerant to
clear the sight glass in the filter drier. (8) At the point when the sight glass clears, note
the weight of the refrigerant supply drum or the
level in the charging cylinder. Then add an addi-
tional 340 g (12 oz) of refrigerant to the system. Re- move the jumper wire from the low pressure cut-off
switch connector and connect the cut-off switch.
(9) Test the over all performance of the air condi-
tioner as described in A/C Overall Performance Test
in this Group. Close all valves on the charging equip-
ment and disconnect the hoses from the service ports
as described in the Manifold Gauge Set Connections
section of this Group. Install the service port caps.
DISCHARGING REFRIGERANT SYSTEM
(R-12) refrigerant is a chlorofluorocarbon (CFC)
that can contribute to the depletion of the ozone
layer in the upper atmosphere. To help protect the
ozone layer, an R-12 refrigerant recycling device
must be used. Use this device when it is necessary to
empty the refrigerant system. Contact an automotive
service equipment supplier for refrigerant recycling
equipment. Refer to the operating instructions pro-
vided with the recycling equipment for proper opera-
tion.
EVACUATING REFRIGERANT SYSTEM
If the A/C system has been open to the atmosphere,
it must be evacuated before the system can be
charged. Moisture and air mixed with the refrigerant
will raise the compressor head pressure above accept-
able operating levels. This will reduce the perfor-
mance of the air conditioner and damage the
compressor. Moisture will boil at near room temper-
ature when exposed to vacuum. To evacuate the re-
frigerant system: (1) Connect a suitable charging station, refrigerant
recovery machine, and a manifold gauge set with
vacuum pump. (2) Open the suction and discharge valves and
start the vacuum pump. When the suction gauge
reads -88 kPa (-26 in. Hg) vacuum or greater, close
all valves and turn off vacuum pump. If the system
fails to reach specified vacuum, the refrigerant sys-
tem likely has a leak that must be corrected. If the
refrigerant system maintains specified vacuum for at
least 30 minutes, start the vacuum pump. Then open
the suction and discharge valves, and allow the sys-
tem to evacuate an additional 10 minutes. (3) Close all valves. Turn off and disconnect the
vacuum pump. The refrigerant system is prepared to be charged
with refrigerant.
CHARGING REFRIGERANT SYSTEMÐEMPTY
SYSTEM
CAUTION: Do not over charge refrigerant system,
as excessive compressor head pressure can cause
noise and system failure.
Fig. 6 Testing for A/C LeaksÐTypical Front/Rear A/C System
Ä HEATING AND AIR CONDITIONING 24 - 11

WARNING: REVIEW SAFETY PRECAUTIONS AND
WARNINGS BEFORE CHARGING THE REFRIGER-
ANT SYSTEM.
After the system has been tested for leaks and
evacuated, a refrigerant charge can be injected into
the system. (1) Connect manifold gauge set.
(2) Measure refrigerant (refer to capacities) and
heat to 52ÉC (125ÉF) with the charging station. Refer
to the instructions provided with the equipment be-
ing used.
REFRIGERANT CAPACITIES:
² Without Rear A/C = 907 g (32 oz.)
² With Rear A/C = 1219 g (43 oz.)
(3) Open the suction and discharge valves. Open
the charge valve to allow the heated refrigerant to
flow into the system. When the transfer of refriger-
ant has stopped, close the suction and discharge
valve. (4) If all of the refrigerant charge did not transfer
from the dispensing device, start engine and hold at
idle (1400 rpm). Set the A/C control to A/C, low
blower speed, and open windows. If the A/C compres-
sor does not engage, test the compressor clutch con-
trol circuit and correct any failure. Refer to Group
8W, Wiring Diagrams. (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. Refer to Heater and A/C Performance Tests
in this Group. (7) Disconnect the charging station or manifold
gauge set. Install the service port caps.
OIL LEVEL
It is important to have the correct amount of oil in
the A/C system to ensure proper lubrication of the
compressor. Too little oil will result in damage to the
compressor. Too much oil will reduce the cooling ca-
pacity of the system. The oil used in the compressor is a 500 SUS viscos-
ity, wax-free refrigerant oil. Only refrigerant oil of
the same type should be used to service the system.
Do not use any other oil. The oil container should be
kept tightly capped until it is ready for use, and then
tightly capped after use to prevent contamination
from dirt and moisture. Refrigerant oil will quickly
absorb any moisture it comes in contact with. It will not be necessary to check oil level in the
compressor or to add oil unless there has been an oil
loss. This may be due to a ruptured line, shaft seal leakage, leakage from the evaporator, condenser
leak, filter drier or loss of refrigerant due to a colli-
sion. Oil loss at a the leak point will be evident by
the presence of a wet, shiny surface around the leak.
REFRIGERANT OIL LEVEL CHECK
When an A/C system is assembled at the factory,
all components (except the compressor) are refriger-
ant oil free. After the system has been charged with
R-12 and operated, the oil in the compressor is dis-
persed through the lines and components. The evap-
orator, condenser, and filter-drier will retain a
significant amount of oil. (Refer to the Refrigerant
Oil Capacities chart). When a component is replaced,
the specified amount of refrigerant oil must be
added. When the compressor is replaced, the amount
of oil that is retained in the rest of the system must
be drained from the replacement compressor. When a
refrigerant line or component has ruptured and it
has released an unknown amount of oil. The A/C
compressor should be removed and drained through
the suction port. The filter-drier must be replaced
along with the ruptured part. Then the oil capacity
of the system (minus the amount of oil still in the re-
maining components) can be poured into the suction
port of the compressor. Example: The evaporator retains 60 ml (2 oz). The
condenser retains 30 ml (1 oz) of oil, and system ca-
pacity may be 214 ml (7.25 oz) of oil. 214 ml minus 90 ml = 124 ml (4.25 oz).
VERIFY REFRIGERANT OIL LEVEL
(1) Using a refrigerant recovery machine, remove
refrigerant from the A/C system. (2) Remove refrigerant lines from A/C compressor.
(3) Remove compressor from vehicle.
(4) From suction port on top of compressor, drain
refrigerant oil from compressor. (5) Add system oil capacity minus the capacity of
components that have not been replaced. Refer to the
Refrigerant Oil Capacity chart. Add oil through suc-
tion port on compressor. (6) Install compressor, connect refrigerant lines,
evacuate, and charge refrigerant system.
REFRIGERANT OIL CAPACITIES
24 - 12 HEATING AND AIR CONDITIONING Ä

VARIABLE DISPLACEMENT COMPRESSORÐMODEL 6C17 INDEX
page page
Clutch Coil Tests ......................... 17
Compressor ............................. 17
Compressor Clutch Inoperative .............. 13
Compressor Clutch/Coil Assembly ............ 19
Compressor Diagnosis ..................... 13
Compressor Front Shaft Seal ............... 20 Compressor High Pressure Cut-Out Switch
..... 21
Compressor High Pressure Relief Valve (HPR) . . 22
Compressor Identification ................... 13
Compressor Main or Sub Control Valves ....... 22
Compressor Noise ........................ 13
General Information ....................... 13
GENERAL INFORMATION
The Variable Displacement Compressor (VDC) pro-
vides maximum A/C performance under most condi-
tions. It is designed to operate continuously without
any cycling of the compressor clutch. The compressor
has a variable angle wobble plate with six axially
oriented cylinders. During vehicle A/C system operation, the compres-
sor will change its displacement to match the vehi-
cles A/C cooling demands. When the A/C system
needs more cooling capacity, the compressor will in-
crease its pumping capacity. This is done by increas-
ing the wobble plate angle to increase the piston
stroke. When the A/C system cooling demand is low,
the compressor will decrease its pumping capacity by
reducing the piston pumping stroke. The low cooling
capacity will prevent evaporator from freezing.
COMPRESSOR IDENTIFICATION
The Variable Displacement Compressor can be
identified by the location of the high pressure line. It
is mounted to the end of the compressor case (Fig. 1).
COMPRESSOR DIAGNOSIS
(1) Verify that refrigerant system is at full charge.
Refer to the Refrigerant Service Procedures section
in this Group. (2) Perform A/C Performance Test. Refer to Heater
and A/C Performance Test section in this Group. (3) If performance is not acceptable, perform ex-
pansion valve tests. Refer to Expansion Valve Tests
in this section. (4) If expansion valve test is correct, refer to the
Variable Displacement Compressor Diagnosis charts.
COMPRESSOR NOISE
Excessive noise that occurs when the air condition-
ing is being used, can be caused by:
² Loose bolts
² Mounting brackets
² Loose clutch
² Excessive high refrigerant system operating pres-
sure Verify compressor drive belt condition, proper re-
frigerant charge and head pressure before compressor
repair is performed. For noise diagnostic procedures, refer to the Com-
pressor Noise and Compressor Clutch Diagnosis
chart in this section.
COMPRESSOR CLUTCH INOPERATIVE
The air conditioning compressor clutch electrical
circuit is controlled by the engine controller. The
controller is located in the engine compartment out-
board of the battery. If the compressor clutch does not engage:
Verify refrigerant charge. Refer to Refrigerant Ser-
vice Procedures in this section. If the compressor clutch still does not engage:
Check for battery voltage at the differential pres-
sure cut-off switch located on the expansion valve. If
voltage is not detected, refer to: (1) Group 8W, Wiring Diagrams.
Fig. 1 Variable Displacement CompressorÐModel 6C17
Ä HEATING AND AIR CONDITIONING 24 - 13