door lock CHEVROLET DYNASTY 1993 Manual Online

mately 50 mm (2 in.) up from bottom rearward cor-
ner of glass through opening in inner door panel.
Push handle of tool toward glass to open channel.
Pull upward at front of glass to separate the slide
from the channel. Do not allow upper slide to snap
bank into channel. (5) Rotate front of glass downward and slide glass
forward to separate glass lift channel from regulator
lift arm roller. (6) Remove door glass through opening at top of
door.
INSTALLATION
(1) Lower door glass into opening at top of door.
(2) Tip rear of glass downward and insert window
regulator lift arm roller into glass lift channel. (3) Guide door glass into glass run weatherstrip at
front of door. (4) Push top of glass rearward to snap top slide
into glass run channel. (5) Push downward at front of glass to snap bottom
slide into glass run channel. (6) Install water shield, silencer pad and trim
panel.
FRONT POWER DOOR LOCK ACTUATOR
REMOVAL (FIG. 14)
(1) Disconnect battery negative cable.
(2) Remove front door trim panel.
(3) Remove water shield as necessary.
(4) Remove rivets holding lock motor to inner door
panel wit ha6mm (1/4 in.) drill.
(5) Disconnect lock motor linkage rod from door
latch. (6) Disconnect lock motor wire connector.
(7) Separate lock motor from door.
INSTALLATION
Reverse the preceding operation.
FRONT DOOR BELT MOULDING AND
WEATHERSTRIP
BELT MOULDING AND WEATHERSTRIP
REMOVAL
(1) Remove trim panel, silencer pad, and water
shield as necessary to gain access to belt moulding
attaching screws. (2) Remove door glass.
(3) Remove screws holding belt moulding and
weatherstrip to outer door panel and separate moul-
ding from door.
BELT MOULDING AND WEATHERSTRIP INSTALLATION
Reverse the preceding operation.
Fig. 12 Front Door Side View MirrorÐTypical
Fig. 13 Front Door Glass
Fig. 14 Front Power Door Lock ActuatorÐTypical
23 - 102 AP-BODY Ä

REAR POWER DOOR LOCK ACTUATOR
REMOVAL (FIG. 24)
(1) Remove door trim panel, silencer pad, and wa-
ter shield. (2) Raise door glass to full up position.
(3) Remove door speaker, if equipped.
(4) Disconnect actuator rod from door latch assem-
bly. (5) Remove screws holding power lock actuator to
inner door panel and separate from door.
INSTALLATION
Reverse the preceding operation.
REAR DOOR GLASS
REMOVAL (FIG. 25)
(1) Remove door trim panel and water shield.
(2) Position door glass half way up in door glass
opening. (3) Pull upward firmly at the front upper corner of
glass to disengage lower glass guide from run chan-
nel. (4) Insert door glass removal tool C-4867 between
the glass slide and division run channel retaining lip
at approximately 50 mm (2 in.) down from top rear-
ward corner of glass. Push handle of tool toward
glass to open channel. Pull forward on the glass to
separate the slide from the channel. (5) Position glass inboard of the division channel.
Pivot top of glass rearward between division channel
and inner door panel. (6) Separate regulator lift arm roller from glass lift
channel or remove bolt from regulator track, with
power windows. (7) Remove door glass through opening at top of
door.
INSTALLATION
(1) Lower door glass into opening at top of door.
(2) Insert window regulator lift arm roller into
glass lift channel or install bolt to regulator track,
with power windows. (3) Push top of glass rearward to snap top slide
into division run channel. (4) Push downward at front of glass to snap bottom
slide into channel. (5) Install water shield and trim panel.
REAR DOOR BELT MOULDING AND
WEATHERSTRIP
REMOVAL
(1) Remove trim panel, silencer pad, and water
shield.
Fig. 23 Rear Door Latch AssemblyÐTypical
Fig. 24-Rear Power Lock ActuatorÐTypical
Fig. 25 Rear Door Glass
23 - 106 AP-BODY Ä

REAR SEAT BACK
REMOVAL (FIG. 28)
(1) Remove seat cushion.
(2) Raise sling well behind quarter trim panels to
gain access to seat back nuts. (3) Reach beneath sling well and remove nuts
holding seat back to support reinforcement. (4) Separate seat back from vehicle.
INSTALLATION
Reverse the preceding operation.
QUARTER TRIM PANEL
REMOVAL (FIG. 29)
(1) Remove bolts holding front outboard seat belt
to floor. Remove cover from belt end. (2) Remove screws holding quarter trim to inner
quarter panel. (3) Remove push-in fastener holding top of door
opening weatherstrip to quarter trim panel. (4) Remove door opening sill plate as necessary to
clear quarter trim. (5) Remove courtesy lamp and disconnect wire con-
nector. (6) Separate trim panel from inner quarter panel
and disconnect speaker wire. (7) Remove bolts holding rear outboard seat belt to
inner quarter panel. (8) Push seat belt end through openings in trim
panel and remove trim panel from vehicle.
INSTALLATION
Reverse the preceding operation.
DOOR STRIKER GUIDE
REMOVAL (FIG. 30)
(1) Remove quarter trim panel as necessary to
gain access to striker guide attachments. (2) Remove nuts holding striker guide to inner
quarter panel. (3) Separate striker guide from lock pillar.
INSTALLATION
Reverse the preceding operation.
FRONT SEAT BELT RETRACTOR
REMOVAL (FIG. 31)
(1) Remove quarter trim panel as necessary to
gain access to seat belt retractor. (2) Remove bolt holding shoulder harness turning
loop to inner quarter panel. (3) Remove bolt holding seat belt retractor to inner
quarter panel. (4) Separate seat belt from vehicle.
Fig. 28 Rear Seat Attaching Nuts
Fig. 29 Quarter Trim Panel
Fig. 30 Door Striker Guide
23 - 128 AP/27 CONVERTIBLE Ä

(3) Mark all bolt and hinge attachment locations
with a grease pencil to provide reference marks for
installation. When installing hinge, align all marks
and secure bolts. The trunk lid should be aligned to 4
mm (.160 in.) gap to the quarter panels and flush
across the top surfaces along quarters. (4) Remove bolts holding hinge to trunk lid and
separate hinge from vehicle.
INSTALLATION
Reverse the preceding operation.
CONVERTIBLE TOP ADJUSTMENTS
When a convertible top component is aligned to
proper fit and finish specifications, weatherstrips and
seals will not always make proper contact. In these
cases, the use of shims, spacers, caulking putty and
foam adhesive backed tape will be required to gain
proper seal compression. Align weatherstrip and seal
channels or retainers so the contact surfaces are
smooth and make full contact with mating surfaces.
A paper strip, equal in size to a dollar bill, should be
able to be drawn through the contact surfaces with-
out tearing the paper. A reasonable amount of effort
should be required to pull the paper through. Bolt on body panels should be aligned to the weld
on body components. The door should be aligned to
the quarter panel, rocker panel and A-pillar. The
gaps between panels should be as equal as possible.
When the door is fitted properly, the door glass can
be aligned to roof rail and A-pillar weatherstrips. Af-
ter verifying the door and door glass alignment, the
quarter glass can be aligned to the door glass and
rear roof rail.
DOOR GLASS ALIGNMENT
GLASS UP-STOP
The door glass up-stop bumper can be adjusted to
raise or lower the glass in the full up position. (1) Remove door trim panel and water shield.
(2) Loosen up-stop bolt.
(3) Adjust bracket.
(4) Tighten up-stop bolt.
DIVISION BAR ALIGNMENT
The rear of the glass can be aligned up or down by
shifting the bottom attachment of the division bar.
Division bar adjustments are small and may not be
possible on some vehicles. (1) Remove door trim panel and water shield.
(2) Loosen blot holding bottom of division bar to
inner door panel. (3) Loosen bolt holding division bar to door inner
panel below stationary glass. (4) Shift division bar forward or rearward to
achieve proper adjustment. (5) Tighten bolts.
CONVERTIBLE TOP LATCH HOOKS
(1) Disengage top latches and raise top halfway.
(2) Loosen set screw locking latch hook in position.
(2) Rotate latch hook in or out to adjust latching
effort and roof header weatherstrip compression. (3) Verify latching effort and tighten set screws.
ROOF RAIL WEATHERSTRIP RETAINER
(1) Disengage top latches and raise top halfway.
(2) Verify that door glass is all the way up and
properly aligned.
Fig. 37 Trunk Lid
Fig. 38 Trunk Lid Hinge
Ä AP/27 CONVERTIBLE 23 - 131

(6) Disengage frog-leg fasteners holding trim panel
to inner door panel. (7) Lift trim panel upward and separate trim from
door. (8) Disconnect courtesy lamp, power door lock
switch and power window switch wire connectors.
TRIM PANEL INSTALLATION
Reverse the preceding operation.
SIDE VIEW MIRROR TRIM COVER
REMOVAL
(1) Remove Front door trim panel.
(2) Disconnect power mirror wire connector.
(3) Remove screws holding mirror trim cover to
door frame.
INSTALLATION
Reverse the preceding operation.
DOOR FRAME TRIM MOULDING
REMOVAL (FIG. 11)
(1) Remove front door trim panel.
(2) Disengage trim clips holding moulding to win-
dow opening frame and separate moulding from door.
INSTALLATION
Reverse the preceding operation.
FRONT DOOR SILENCER AND WATER SHIELD
REMOVAL
(1) Remove front door trim panel.
(2) Pull water shield from adhesive around perim-
eter of door inner panel.
INSTALLATION
Reverse the preceding operation.
FRONT DOOR AND HINGE
The front door hinge is welded to the door and
bolted to the hinge pillar. The door half of the hinge
pivots on a removable hinge pin. The hinge pin is
driven in from the bottom on the top hinge and from
the top on the bottom hinge. All adjustments to the
hinge are performed on the hinge pillar half of the
hinge. If the welded half of the hinge must be bent to
align door, consult an authorized body repair facility.
FRONT DOOR REMOVAL (FIG. 12)
(1) Remove door trim panel, silencer pad, and wa-
ter shield. (2) Disconnect all wire connectors and wire har-
ness hold downs inside door and push wire harness
through access hole in front of door into hinge pillar
opening. (3) Open door and support door on a suitable lift-
ing device. (4) Drive bottom hinge pin upward and remove pin
from hinge. (5) Drive top hinge pin downward and remove pin
from hinge.
FRONT DOOR INSTALLATION
Reverse the preceding operation. The door should
not require re-alignment. If door does need align-
ment, refer to Front Door Hinge Installation para-
graph in this section.
FRONT DOOR HINGE REMOVAL (FIG. 12)
(1) Remove front fender wheelhouse splash shield.
Refer to Front Wheelhouse Splash Shield Removal
paragraph in this section. (2) Support door on a suitable lifting device.
(3) Drive out hinge pin on the effected hinge.
Fig. 10 Engine Drive Belt Splash ShieldÐTypical
Fig. 11 Front Door Trim Panel
Ä AY-BODY 23 - 137

(4) Remove bolts holding hinge to hinge pillar and
separate hinge form vehicle.
FRONT DOOR HINGE INSTALLATION
Reverse the preceding operation. Align door to
achieve 6 mm (0.240 in.) gap to all surrounding pan-
els and flush across gaps.
OUTSIDE DOOR HANDLE
REMOVAL (FIG. 13)
(1) Remove door trim panel.
(2) Remove silencer pad and water shield as neces-
sary. (3) Raise door glass to up position.
(4) Disconnect illuminated entry wire connector
from outside door handle assembly, if equipped. (5) Disconnect latch release linkage from latch as-
sembly. (6) Disconnect lock cylinder linkage from latch as-
sembly. (7) Remove nuts holding outside handle bracket to
door panel and separate bracket from panel. (8) Position linkage rods parallel to the back of
handle and remove handle assembly from door.
INSTALLATION
Reverse the preceding operation.
FRONT DOOR LATCH
REMOVAL (FIG. 14)
(1) Remove door trim panel.
(2) Remove silencer pad and water shield as neces-
sary. (3) Disconnect linkage rods from door latch assem-
bly. (4) Remove screws holding latch door end frame.
(5) Separate latch from door.
INSTALLATION
Reverse the preceding operation.
FRONT DOOR WINDOW REGULATOR
REMOVAL (FIG. 15 OR 16)
MANUAL OR ELECTRIC
(1) Remove front door trim panel.
(2) Remove silencer pad and water shield.
(3) Remove side view mirror trim cover and door
frame trim moulding.
Fig. 12 Front Door Assembly
Fig. 13 Front Door Handle Assembly
Fig. 14 Front Door Latch Assembly
23 - 138 AY-BODY Ä

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

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

(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