1993 CHEVROLET DYNASTY service

(5) Evacuate and charge the refrigerant system. If
oil loss of 3 ml (1 oz) or greater is suspected, refer to
Oil Level in the Refrigerant Service Procedures sec-
tion.
COMPRESSOR HIGH PRESSURE CUT-OUT SWITCH
The High Pressure Cut Out (HPCO) switch is lo-
cated on the rear cover of the Variable Displacement
Compressor (Fig. 6). The function of the switch is to disengage the compressor clutch by monitoring the
compressor discharge (high) pressure. The HPCO
Switch is in the same circuit as the Differential Pres-
sure Cut Out (DPCO) switch and Ambient Switch.
DIAGNOSIS
Review Safety Precautions and Warnings before
proceeding with this operation. Connect a suitable manifold gauge set to the refrig-
erant system service ports. Work area temperature
can not be below 21ÉC (70ÉF). (1) Raise hood of vehicle.
(2) With gear selector in park or neutral, and park
brake set, start engine and allow to idle at 1300 rpm. (3) Set the A/C controls to A/C and High blower.
(6) If the high pressure gauge reads below 2963
kPa (430 psi) 6138 kPa (20 psi) the compressor
clutch should be engaged.
CAUTION: Do not allow engine to overheat when ra-
diator air flow is blocked.
(7) Block radiator air flow with a suitable cover to
increase the high side pressure to at least 3100 kPa
(450 psi). Compressor clutch should disengage. (8) Remove cover from front of vehicle to allow
high side pressure to decrease. When pressure drops
below 1826 kPa (265 psi), compressor clutch should
engage.
REMOVAL AND INSTALLATION
(1) Using a refrigerant recovery machine, remove
the refrigerant from the A/C system.
Fig. 3 Remove Shaft Seal
Fig. 4 Shaft Seal Protector
Fig. 5 Install Shaft Seal
Fig. 6 Variable Displacement CompressorÐModel 6C17
Ä HEATING AND AIR CONDITIONING 24 - 21

(2) Disconnect wire connector from the high pres-
sure cut-out switch (Fig. 7).
(3) Remove snap ring securing the switch in the
compressor end cover (Fig. 8).
CAUTION: The high pressure cut-out switch service
kit has two snap rings. One is black and the other
is silver. Use the one which has the same color as
the original one in the compressor.
(4) Pull switch straight out from end cover. Re-
move and discard used O-ring seal (Fig. 9). To install, reverse the preceding operation using a
new O-ring seal. Evacuate and charge the refrigerant
system.
COMPRESSOR HIGH PRESSURE RELIEF VALVE
(HPR)
DIAGNOSIS
The High Pressure Relief valve prevents damage to
the air conditioning system if excessive pressure de-
velops. Excessive pressure may be caused by con- denser air flow blockage, refrigerant overcharge, or
air and moisture in the system.
The High Pressure Relief valve vents only a small
amount of refrigerant necessary to reduce system
pressure and then reseats itself. The majority of the
refrigerant is conserved in the system. The valve is
calibrated to vent at a pressure of 3100 to 4140 Kpa
(450 to 600 psi). If a valve has vented a small
amount of refrigerant, it does not necessarily mean
the valve is defective.
VALVE LOCATION
The High Pressure Relief Valve is located on the
compressor end plate.
REMOVAL AND INSTALLATION
(1) Using a refrigerant recovery machine, remove
the refrigerant from the A/C system. (2) Rotate the high pressure relief valve counter-
clockwise and separate relief valve from the vehicle
(Fig. 10). To install, reverse the preceding operation using a
new O-ring seal. Evacuate and charge the refrigerant
system.
COMPRESSOR MAIN OR SUB CONTROL VALVES
If the main or sub control valve is leaking refrig-
erant to the atmosphere, replace the main or sub
control valve. If a functional problem is suspected
with the main or sub control valve, the compressor
should be replaced.
REMOVAL AND INSTALLATION
(1) Using a refrigerant recovery machine, remove
the refrigerant from the A/C system. (2) Remove the compressor assembly. Position it to
gain access to the control valves. It is not necessary
to disconnect the suction or discharge lines from the
compressor.
Fig. 7 High Pressure Cut-out Switch
Fig. 8 Remove or Install Snap Ring
Fig. 9 Remove or Install High Pressure Cut-out Switch
24 - 22 HEATING AND AIR CONDITIONING Ä

FIXED DISPLACEMENT COMPRESSORÐMODEL 10PA17 INDEX
page page
Compressor ............................. 24
Compressor Clutch/Coil Assembly ............ 24
Compressor Front Shaft Seal ............... 27 Compressor High-Pressure Relief Valve
....... 30
Refrigerant System Diagnosis ............... 30
COMPRESSOR
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.
REMOVAL AND INSTALLATION
The A/C compressor may be removed and posi-
tioned without discharging the refrigerant system.
Discharging is not necessary if removing the A/C
compressor clutch/coil assembly, engine, cylinder
head, or generator.
WARNING: REFRIGERANT PRESSURES REMAIN
HIGH EVEN THOUGH THE ENGINE MAY BE
TURNED OFF. BEFORE REMOVING A FULLY
CHARGED COMPRESSOR, REVIEW THE SAFETY
PRECAUTIONS AND WARNINGS SECTION IN THIS
GROUP. DO NOT TWIST OR KINK THE REFRIGER-
ANT LINES WHEN REMOVING A FULLY CHARGED
COMPRESSOR. SAFETY GLASSES MUST BE
WORN.
(1) Disconnect Negative battery cable.
(2) Loosen and remove drive belts (refer to Group
7, Cooling System) and disconnect compressor clutch
wire lead. (3) Remove refrigerant lines from compressor (if
necessary). (4) Remove compressor attaching nuts and bolts.
(5) Remove compressor. If refrigerant lines were
not removed, lift compressor/clutch assembly and tie
it to a suitable component. To install, reverse the preceding operation. If nec-
essary, refer to Charging Refrigerant System in the
Refrigerant Service Procedures section.
COMPRESSOR CLUTCH/COIL ASSEMBLY
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.
If the compressor clutch still does not engage check
for battery voltage at the low pressure or differential
pressure cut-off switch located on the expansion
valve. If voltage is not detected, refer to:
² Group 8W, Wiring Diagrams.
² The appropriate Powertrain Diagnostic Procedures
Manual for diagnostic information. If voltage is detected at the cut-off switch, recon-
nect switch. Then check for battery voltage between
the compressor clutch connector terminals. If voltage is detected, perform A/C Clutch Coil
Tests.
CLUTCH COIL TESTS
(1) Verify battery state of charge. (Test indicator
in battery should be green). (2) Connect an ammeter (0-10 ampere scale) in se-
ries with the clutch coil terminal. Use a volt meter
(0-20 volt scale) with clip leads measuring voltage
across the battery and A/C clutch. (3) With A/C control in A/C mode and blower at
low speed, start the engine and run at normal idle. (4) The A/C clutch should engage immediately and
the clutch voltage should be within two volts of the
battery voltage. If the A/C clutch does not engage,
test the fusible link. (5) The A/C clutch coil is acceptable if the current
draw is 2.0 to 3.7 amperes at 11.5-12.5 volts at clutch
coil. This is with the work area temperature at 21ÉC
(70ÉF). If voltage is more than 12.5 volts, add electri-
cal loads by turning on electrical accessories until
voltage reads below 12.5 volts. If coil current reads zero, the coil is open and
should be replaced. If the ammeter reading is 4 am-
peres or more, the coil is shorted and should be re-
placed. If the coil voltage is not within two volts of
the battery voltage, test clutch coil feed circuit for
excessive voltage drop.
24 - 24 HEATING AND AIR CONDITIONING Ä

FIXED DISPLACEMENT COMPRESSORÐMODEL SD709P INDEX
page page
Compressor ............................. 38
Compressor Clutch/Coil Assembly ............ 38
Compressor Shaft Seal .................... 41 Cylinder Head/Valve Plate
.................. 44
Description ............................. 38
Refrigerant System Diagnosis ............... 45
DESCRIPTION
The Sanden compressor is a 7 piston design. Sys-
tem lubrication is provided by 135 ml 615 ml (4.6 oz.
6 0.5 oz.) of 500 viscosity refrigerant oil.
The clutch used on the compressor consists of 3 ba-
sic components:
² The pulley
² Front plate
² Field coil
The pulley and field coil are attached to the front
head of the compressor with tapered snap rings. The
hub is keyed to the compressor shaft and is retained
on the shaft with a self-locking nut. Special service
tools are required to remove and install the clutch
plate on the compressor shaft.
COMPRESSOR
The A/C compressor may be removed and posi-
tioned without discharging the refrigerant system.
Discharging is not necessary if removing the A/C
compressor clutch/coil assembly, engine, cylinder
head, or generator.
WARNING: REFRIGERANT PRESSURES REMAIN
HIGH EVEN THOUGH THE ENGINE MAY BE
TURNED OFF. BEFORE REMOVING A FULLY
CHARGED COMPRESSOR, REVIEW THE SAFETY
PRECAUTIONS AND WARNINGS SECTION IN THIS
GROUP. DO NOT TWIST OR KINK THE REFRIGER-
ANT LINES WHEN REMOVING A FULLY CHARGED
COMPRESSOR. SAFETY GLASSES MUST BE
WORN.
REMOVAL
(1) Disconnect negative cable from battery.
(2) Loosen and remove drive belts (refer to group
7, Cooling System) and disconnect compressor clutch
wire lead. (3) Remove refrigerant lines from compressor (if
necessary). (4) Remove compressor attaching nuts and bolts.
(5) Remove compressor. If refrigerant lines were
not removed, lift compressor/clutch assembly and tie
it to a suitable component. To install, reverse the removal procedure.
COMPRESSOR CLUTCH/COIL ASSEMBLY
The magnetic clutch consists of a stationary elec-
tro-magnetic coil and a rotating pulley and plate as-
sembly. The electromagnetic coil is retained on the com-
pressor with a snap ring and is dimpled to maintain
its position. The pulley and plate assembly are mounted on the
compressor shaft. When the compressor is not in operation, the pul-
ley free wheels on the clutch hub bearing. When the
coil is energized the plate is magnetically engaged
with the pulley and turns the compressor shaft.
REMOVAL
(1) Insert the 2 pins of the front plate spanner into
any 2 threaded holes of the clutch front plate (Fig.
1). Hold clutch plate stationary. Remove hex nut
with 19 mm (3/4 inch) socket.
(2) Remove clutch front plate using puller. Align
puller center bolt to compressor shaft (Fig. 2). Thumb
tighten the puller bolts into the threaded holes. (3) Turn center bolt clockwise with 19 mm (3/4
inch) socket until front plate is loosened. (4) Remove shaft key by lightly tapping it loose
with a slot screwdriver and hammer (Fig. 3). (5) Remove the external front housing snap ring
by using spread type snap ring pliers (Fig. 4).
Fig. 1 Hex Nut Removal
24 - 38 HEATING AND AIR CONDITIONING Ä

COMPONENT SERVICE PROCEDURES INDEX
page page
Air Distribution Duct ...................... 50
Air Distribution Duct ...................... 52
Ambient Switch .......................... 47
Blend-Air Door .......................... 64
Blower Motor ............................ 58
Blower Motor Wheel Assembly .............. 58
Blower Resistor Block ..................... 49
Condensate Drain Tube ................... 64
Condenser Assembly ...................... 57
Condenser Fan Control Switch .............. 47
Defroster Duct ........................... 51
Defroster Duct Adapter .................... 51
Defroster Ducts/Demister Ducts and Hoses ..... 52
Differential Pressure Cut-Out Switch Diagnosis . . 48
Evaporator Coil .......................... 64 Expansion Valve
......................... 55
Filter-Drier Assembly ...................... 57
Fin-Sensing Cycling Clutch Switch ............ 53
Heater Core ............................ 64
Heater Hoses ........................... 51
Heater-A/C Unit AssemblyÐRemoval and Installation ............................ 61
Heater-A/C Unit Recondition ................ 63
Low or Differential Pressure Cut-Off Switch ..... 54
Temperature Control CableÐAA,AP,AG and AJ Models ............................ 49
Temperature Control CableÐAC/AY Models .... 48
Vacuum ActuatorÐFresh/Recirc Door ......... 50
Vacuum ActuatorsÐMode Doors ............. 52
AMBIENT SWITCH
The ambient switch is a temperature sensor located
in front of the condenser behind the grille (Fig. 1).
The ambient switch prevents the compressor from
engaging in cold temperatures. The ambient switch
is a sealed factory calibrated unit. It must be re-
placed if defective.
AMBIENT SWITCH TEST
(1) Disconnect ambient switch wire connector.
(2) Using a suitable ohm meter or continuity
tester, test for continuity across the ambient switch
terminals. (a) At temperature above 10ÉC (50ÉF), the switch
circuit should be complete. (b) Chill the switch with ice to below 10ÉC (50ÉF)
and test for continuity. The switch circuit should
be open, with continuity not detected.
Replace ambient switch if defective.
REMOVAL AND INSTALLATION
(1) Remove the one attaching screw.
(2) Remove the sensor/bracket assembly from the
vehicle. To install, reverse the preceding operation.
CONDENSER FAN CONTROL SWITCH
The Fan Control Switch is located on the plumbing
discharge line at the A/C compressor (Fig. 2). The fan
control switch cycles the radiator/condenser fan on and
off by monitoring the compressor discharge pressure.
The radiator top tank temperature sensor can over ride
the function of the fan control switch. It can cycle the
radiator/condenser fan on and off depending on the
engine temperature.
FAN CONTROL SWITCH DIAGNOSIS
Review Safety Precautions and Warnings before pro-
ceeding. Connect a manifold gauge set to the refriger-
ant system service ports. Work area temperature can
not be below 21ÉC (70ÉF).
Fig. 1 Ambient Temperature Sensor SwitchÐTypical Mounting
Fig. 2 Condenser Fan Control Switch
Ä HEATING AND AIR CONDITIONING 24 - 47

WARNING: AVOID RADIATOR/CONDENSER FAN
BLADES WHEN WORKING IN THE RADIATOR
AREA. FAN IS CONTROLLED BY TEMPERATURE
AND CAN START ANY TIME IGNITION IS ON. PER-
SONAL INJURY CAN RESULT.
(1) Disconnect fan control switch wire connector.
(2) Using a suitable jumper wire, jump across ter-
minals in wire connector. (3) Connect a suitable continuity tester across fan
control switch terminals. (4) Start engine and set idle at 1300 rpm. The ra-
diator fan should run constantly. (5) Set the A/C controls to A/C and high blower.
(6) If the high pressure gauge reads below 1102
kPa (160 psi) there should be no continuity across
the switch terminals.
CAUTION: Do not allow engine to overheat when ra-
diator air flow is blocked.
(7) Block radiator air flow with a suitable cover to
increase the high side pressure to at least 1585 kPa
(230 psi). Electrical continuity should be detected
across the fan control switch terminals. (8) Remove cover from front of vehicle to allow
high side pressure to decrease. When pressure drops
below 1102 kPa (160 psi), continuity should cease. If fan control switch is defective, replace it.
REMOVAL AND INSTALLATION
CAUTION: Refrigerant removal is not necessary
when removing the Condenser Fan Control Switch.
However, a small amount of refrigerant will vent
from the switch port. Review the refrigerant han-
dling section of Safety Precautions and Warnings in
the General Information section of this Group.
(1) Disconnect wire connector from condenser fan
control switch. (2) Loosen and quickly rotate the switch counter-
clockwise and separate from the high pressure line
switch port. To install, reverse the preceding operation.
DIFFERENTIAL PRESSURE CUT-OUT SWITCH
DIAGNOSIS
The Differential Pressure Cut-Out (DPCO) Switch
(Fig. 3) monitors the liquid refrigerant pressure on
the liquid side of the system. The DPCO is located on
the expansion valve. The expansion valve is black in
color when a variable displacement compressor is
used. The DPCO turns off voltage to the compressor
clutch coil when liquid refrigerant pressure drops to
levels that could damage the compressor. The DPCO
is a sealed factory calibrated unit. It must be re-
placed if defective.
DPCO SWITCH DIAGNOSIS
The work area must not be below 10ÉC (50ÉF) to
test the compressor clutch circuit. (1) With gear selector in park or neutral, and park
brake set, start engine and allow to idle. (2) Raise hood and disconnect DPCO switch con-
nector boot. (3) Using a suitable jumper wire, jump across the
terminals inside wire connector boot. (4) If clutch does not engage, the wiring, fuse, re-
lay, ambient switch, or high pressure cut-off switch
can be defective. Refer to Group 8W, Wiring Dia-
grams. (5) If clutch engages, connect a suitable manifold
gauge set. Read low pressure gauge. At pressure 283
kPa (41 psi) and above, DPCO switch will complete
the clutch circuit. If the low pressure gauge reads be-
low 317 kPa (46 psi), the system is low on refrigerant
charge or empty due to a leak. Refer to Testing For
Refrigerant Leaks in the Refrigerant Service Proce-
dures section. (6) Install connector boot on switch and repeat step
number 3. If the clutch does not engage, replace the
DPCO switch.
TEMPERATURE CONTROL CABLEÐAC/AY MODELS
REMOVAL AND INSTALLATION
A Temperature Control Cable is used on non-ATC
heat or heater-A/C systems only. ATC (Automatic
Temperature Control) systems use an electrically op-
erated temperature control. Refer to the ATC section
of this Group. (1) Remove the A/C-Heater control panel assembly.
Refer to A/C-Heater Control Replacement in Group
8E Instrument Panel. Disconnect the cable attaching
flag from the A/C-heater control and remove the ca-
ble from control panel.
Fig. 3 Differential Pressure Cut-Out Switch
24 - 48 HEATING AND AIR CONDITIONING Ä

(2) Locate and disconnect the cable attaching flag
on the bottom of the A/C-heater housing behind the
floor air duct (Fig. 4).
(3) Slip cable self-adjusting clip downward from
the blend-air door crank. (4) Insert a 3/16 diameter tool (drill bit or phillips
screwdriver shank) into the crank pin access hole
and rotate the clip from the cable. To install, reverse the preceding operation.
To adjust temperature cable, position the TEMP le-
ver on the control to the cool side of its travel. Al-
lowing the self-adjusting clip to slide on the cable,
rotate the blend-air door crank counterclockwise by
hand until it stops.
TEMPERATURE CONTROL CABLEÐAA,AP,AG AND
AJ MODELS
REMOVAL AND INSTALLATION
(1) Remove heater-A/C control panel. Refer to
Switch and Panel Component Service in Group 8E,
Instrument Panel. Disconnect the attaching flag on
the control cable from the heater-A/C control panel. (2) Remove console assembly. Refer to Group 8E,
Instrument Panel. (3) Remove instrument panel lower steering col-
umn cover. Refer to Group 8E, Instrument Panel. (4) Remove the right lower instrument panel/glove
box door assembly. This assembly is clipped to the
upper instrument panel at the right upper side. (5) A/C equipped vehicles: From under the hood,
disconnect the A/C suction line mounting bracket
from the dash panel (above the expansion valve). (6) From under the hood, loosen (do not remove)
the four heater-A/C assembly to dash panel mount-
ing nuts. (7) From inside the vehicle: Remove the vertical
(heater-A/C housing) support bracket (below the
glove box). (8) Tilt the entire heater-A/C housing assembly
downward to gain access to the temperature cable. (9) Locate and disconnect the attaching flag on the
control cable at the heater-A/C housing (Fig. 5). (10) Slip the cable self-adjusting clip from the
blend-air door crank (Fig. 5). (11) Remove the cable from the vehicle.
(12) To remove the self-adjusting clip from cable
(Fig. 5): (a) Insert a 4mm (3/16 inch) diameter drill bit
(Fig. 1-Inset) into the door crank access hole. Then
rotate the clip from the cable.
To install, reverse the preceding operation.
To adjust temperature cable: Position the TEMP le-
ver on the control to the cool side of its travel. Al-
lowing the self-adjusting clip to slide on the cable,
rotate the blend-air door crank counterclockwise by
hand until it stops.
BLOWER RESISTOR BLOCK
WARNING: STAY CLEAR OF THE BLOWER MOTOR
AND RESISTOR BLOCK (HOT) DURING THE FOL-
LOWING PROCEDURES.
CAUTION: Do not operate the blower motor with the
resistor block removed from the heater-A/C hous-
ing. Air must move over the hot coils.
CAUTION: Disconnect battery before performing
this operation.
REMOVE AND INSTALL
AJ AND AG BODY
(1) Remove the instrument panel glove box and
door assembly. Refer to Group 8E Instrument Panel. (2) Remove security and lamp outage modules.
(3) Locate the blower resistor block (Fig. 6). It is
above and to the front of the glove box opening on
the dash panel. Remove the wire connector. (4) Remove the two attaching screws at the resis-
tor block.
Fig. 4 Temperature Control CableÐTypical
Fig. 5 Temperature Control CableÐTypical
Ä HEATING AND AIR CONDITIONING 24 - 49

(5) Carefully pull the resistor block straight out
from the cowl plenum opening and remove the resis-
tor block from the vehicle. To install, reverse the preceding operation. The
coils on the Resistor Block should not be contacting
one another. Before installation, gently separate the
coils (with fingers only) if one coil is contacting an-
other.
AA, AP, AY, AND AC BODY
(1) Raise the hood and remove the windshield
wiper arm assemblies. (2) Remove five cowl-plenum grille attaching
screws and carefully lift the grille from the vehicle. (3) (AA and AP): Locate and remove four air in-
take shield attaching screws and lift the shield from
the vehicle. (4) (AC and AY): Remove two resistor block termi-
nal cover screws and remove cover. (5) Disconnect the wire connector from the resistor
block located behind the windshield washer reservoir
(Fig. 7).
(6) Remove two blower resistor block attaching
screws. Then carefully pull the resistor block forward
until the coils clear the plenum and lift it from the
vehicle. To install, reverse the preceding operation. The
coils on the Resistor Block should not be contacting
one another. Before installation, gently separate the
coils (with fingers only) if one coil is contacting an-
other.
VACUUM ACTUATORÐFRESH/RECIRC DOOR
This actuator is located on the passenger side of
the heater-A/C housing.
REMOVAL AND INSTALLATION
(1) AA, AC or AY Body: Remove silencer cover un-
der the instrument panel (below glove box). (2) Remove glove box assembly. Refer to Group 8E,
Instrument Panel. (3) Disconnect vacuum lines.
(4) Locate and remove the two vacuum actuator at-
taching screws. (5) Disengage the actuator arm linkage from the
door pivot and remove the vacuum actuator (Fig. 8)
from vehicle.
To install, reverse the preceding operation.
AIR DISTRIBUTION DUCT
REMOVAL AND INSTALLATION
AA BODY On AA Body the instrument panel must be rolled
down to service duct. Refer to Group 8E, Instrument
Panel.
AC, AP, AY BODY (1) Remove lower instrument panel module. Refer
to Group 8E, Instrument Panel. (2) Remove distribution duct attaching screws from
under the front edge of the instrument panel (Fig. 9). (3) Slide duct downward and remove from vehicle.
To install, reverse the preceding operation.
Fig. 6 Blower Resistor Block LocationÐAJ and AG Body
Fig. 7 Blower Resistor Block LocationÐAA, AP, AYand AC Body
Fig. 8 Recirculating Air Door VacuumActuatorÐTypical
24 - 50 HEATING AND AIR CONDITIONING Ä