1993 CHEVROLET DYNASTY sensor

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Page 2234 of 2438

CHEVROLET DYNASTY 1993 Service Manual (2) Disengage clips holding expansion trim panel
to shelf panel. (3) Separate trim panel from vehicle.
INSTALLATION
Reverse the preceding operation.
REAR SHELF TRIM PANEL
REMOVAL (FIG. 13)
(1) Remove

Page 2266 of 2438

CHEVROLET DYNASTY 1993 Service Manual (4) Remove screws holding rear header moulding
to roof as necessary to clear quarter removal path. (5) Remove screws holding upper quarter trim
panel to quarter panel. (6) Disengage hook and loop fas

Page 2300 of 2438

CHEVROLET DYNASTY 1993 Service Manual (6) Pull trim panel forward and separate from ve-
hicle. (7) Remove bolt holding lap belt anchor to floor
and push end of belt through access hole in trim
panel.
INSTALLATION
Reverse the preceding op

Page 2351 of 2438

CHEVROLET DYNASTY 1993 Service Manual COMPONENT SERVICE PROCEDURES INDEX
page page
Air Distribution Duct ...................... 50
Air Distribution Duct ...................... 52
Ambient Switch .......................... 47
Blend-A

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

Page 2357 of 2438

CHEVROLET DYNASTY 1993 Service Manual FIN-SENSING CYCLING CLUTCH SWITCH
The Fin-Sensing Cycling Clutch Switch (FCCS)
(Fig. 17) is located in the heater-A/C unit housing
near the blower motor and placed in the evaporator
fins. The FCCS pr

FIN-SENSING CYCLING CLUTCH SWITCH
The Fin-Sensing Cycling Clutch Switch (FCCS)
(Fig. 17) is located in the heater-A/C unit housing
near the blower motor and placed in the evaporator
fins. The FCCS prevents evaporator condensate
freeze-up. This is done by cycling the compressor
clutch OFF when evaporator temperature drops be-
low freeze point. It cycles ON when the evaporator
temperature rises above freeze point. The FCCS uses
a thermistor probe in a capillary tube inserted be-
tween the evaporator fins in the heater-A/C unit
housing. If the compressor clutch does not cycle, and
all other clutch circuit components test correct, test
the switch. At temperatures above 32ÉC (90ÉF) the compressor
clutch may engage continuously and not cycle. This
is due to evaporator temperature above the freezing
point.
DIAGNOSIS
The work area and vehicle must be between 21ÉC
(70ÉF) and 32ÉC (90ÉF) when testing the Fin-sensing
Cycling Switch. (1) Disconnect the 3-wire connector from switch
lead located behind the glove box. (2) Test for voltage between pin #1 to pin #3 on
the wire harness connector (Fig. 18). If voltage is not
detected, refer to the Front Wheel Drive Car-Wiring
Diagrams Service Manual. If voltage is detected,
jump pin #1 to pin #3 using a jumper wire. Com-
pressor clutch should engage.
(3) If compressor clutch engages, test for continuity
from terminal pin #1 to pin #3 of the switch lead
connector. Continuity should be detected. If not, re-
place the Fin-sensing Cycling Clutch Switch.
REMOVAL AND INSTALLATION
(1) Remove the cover/housing from the heater-A/C
blower motor. Refer to Blower Motor removal and in-
stallation. Remove the cover only. Blower motor or
blower motor wheel removal is not necessary. (2) Disconnect the (three pin) wiring pigtail con-
nector from the clutch switch sensor harness (located
on the outside of the A/C-heater housing). Push the
wire harness grommet (attached to the A/C-heater
Fig. 15 Air Distribution Duct
Fig. 16 Defroster Ducts/Demister Ducts and Hoses
Fig. 17 Fin-sensing Cycling Clutch Switch
Fig. 18 Fin-sensing Cycling Clutch Switch Harness Connector
Ä HEATING AND AIR CONDITIONING 24 - 53

Page 2370 of 2438

CHEVROLET DYNASTY 1993 Service Manual AUTOMATIC TEMPERATURE CONTROL (ATC) INDEX
page page
Ambient Temperature Sensor ............... 67
ATC Computer/Control Panel ................ 66
Blend-Air Door Actuator .................... 69

AUTOMATIC TEMPERATURE CONTROL (ATC) INDEX
page page
Ambient Temperature Sensor ............... 67
ATC Computer/Control Panel ................ 66
Blend-Air Door Actuator .................... 69
Computer Aided Diagnostic Tests ............ 72
Diagnostic Trouble Code Definitions .......... 73
Diagnostic Trouble Code Service Procedures . . . 74
Erasing Diagnostic Trouble Codes ............ 83
Fresh/Recirc Door Actuator ................. 68 General InformationÐComponent Operation
.... 66
In-Car Temperature Sensor/Aspirator Assembly . . 70
Manual A/C Mode ........................ 66
Mode Door Actuator ...................... 69
NonÐComputer Aided Diagnostic Tests ....... 72
Power Module ........................... 67
Sun Sensor ............................. 71
Water Temperature Sensor ................. 71
GENERAL INFORMATIONÐCOMPONENT
OPERATION
The Automatic Temperature Control (ATC) system
lets the operator change the passenger compartment
environment. A computer, built into the control
panel (Fig. 1), regulates the desired temperature, air
flow direction and blower speed. The operator may
select an AUTO or MANUAL by using the mode but-
ton. Refer to the Owner's Manual for proper opera-
tion.
The system goes into a maximum cool recirculated
air lock-in mode:
² After selecting a comfort temperature setting of
18ÉC or 65ÉF.
² With the A/C compressor turned ``ON''. The snow-
flake will only illuminate when the system is in the
manual mode.
² With the system not in the defrost mode.
² When the temperature button is held in for ten
seconds. This will not regulate the temperature until the
system is turned off or the comfort setting is raised
(Fig. 2). Vacuum is not used to control any of the ATC sys-
tem or components. It is a totally electronic unit. The A/C compressor can not be turned off in the
AUTO mode.
MANUAL A/C MODE
The manual mode can be activated by pressing the
mode button. The compressor can only be turned
OFF when the climate control system is in the man-
ual mode. The snowflake will be illuminated when
the compressor is ON. The display panel will show LO, 1-10, and HI sym-
bols when in the manual mode.
ATC COMPUTER/CONTROL PANEL
The ATC computer controller (Fig. 3) manages all
of the systems electronic functions. It provides logic
and/or power to operate the power module, blend-air
door actuator, the mode door and fresh/recirc actua-
tors. It remembers the operators control panel se-
lected settings when the vehicle is not running. Then
it measures return inputs from the sun sensor and
various temperature sensors. After measuring all in-
put information, the computer will ground the output
circuits. This provides logic signals for automatic sys-
Fig. 1 Automatic Temperature Control Computer Panel
Fig. 2 Automatic Temperature Control Panel Display Symbols
24 - 66 HEATING AND AIR CONDITIONING Ä

Page 2371 of 2438

CHEVROLET DYNASTY 1993 Service Manual tem control. The computer control panel is not ser-
viceable except for the illumination bulbs. For bulb replacement, refer to A/C-Heater Control
Lamp Replacement in Group 8E Instrument Panel. The A

tem control. The computer control panel is not ser-
viceable except for the illumination bulbs. For bulb replacement, refer to A/C-Heater Control
Lamp Replacement in Group 8E Instrument Panel. The ATC Computer/Control Panel is located in the
center of the instrument panel above the radio.
REMOVAL AND INSTALLATION
Refer to A/C-Heater control replacement in the
Switch and Panel Component section of Group 8E,
Instrument Panel and Gauges.
POWER MODULE
The power module (PM) (Fig. 4) receives pulse
width modulated logic signals from the computer
control. The PM then supplies varied voltage to the
blower motor ground circuit for different blower
speeds based on the logic signal. The power module
is not serviceable and must be replaced if found to be
defective.
REMOVAL AND INSTALLATION
(1) Disconnect the negative battery cable.
(2) Remove glove box/ash tray assembly. Refer to
Switch and Panel Component Service section of
Group 8E. (3) Remove the four PM attaching screws (Fig. 5).
(4) Disconnect electrical connector.
(4) Gently extract PM (to prevent damage to A/C
evaporator) from A/C-heater housing and remove
from under instrument panel. To install, reverse the preceding operation. Perform
systems check.
AMBIENT TEMPERATURE SENSOR
The ambient air temperature sensor is located in
the A/C housing above the glove box. This is also a
thermistor and will pick up on the environmental
ambient temperature. The computer control uses the
information provided by the ambient sensor to:
² Regulate the low blower speed
² Temperature offsets
² Mode control
The ambient sensor is not serviceable and must be
replaced if found to be defective. The ambient temperature sensor is plugged into a
two wire receptacle in the A/C-heater housing behind
and above the glove box.
REMOVAL AND INSTALLATION
(1) Remove glove box/ash tray assembly.
(2) Locate and remove two attaching screws on
sensor receptacle (Fig. 6). (3) Carefully pull receptacle and sensor from hous-
ing.
CAUTION: It is possible for the sensor to hang up
on the edge of the hole in the A/C-heater housing
assembly during removal. This may cause the sen-
sor to disengage from the receptacle and fall into
the housing.
Fig. 3 ATC Computer ControllerÐAspirator Air Intake
Fig. 4 Power ModuleÐAmbient TemperatureSensorÐFresh/Recirc Door Actuator
Fig. 5 Power Module Removal and Installation
Ä HEATING AND AIR CONDITIONING 24 - 67

Page 2372 of 2438

CHEVROLET DYNASTY 1993 Service Manual (4) Unplug sensor from receptacle.
To install, reverse the preceding operation and
retest system.
FRESH/RECIRC DOOR ACTUATOR
The fresh/recirc door actuator is an electric servo
motor. It (with the us

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