1988 PONTIAC FIERO clutch

1988
SER
This manual applies to the 1988 Pontiac Firebird Models.
It contains the latest product information available at the
time of publication approval. lnformation pertaining to
the operation of the vehicle is contained in the Owner's
Manual which accompanies each vehicle. The right is
reserved to make changes at any time without notice.
Any references to brand names in this manual is intended
merely as an example of the types of
lubricant% tools,
materials, etc, recommended for use in servicing 1988
Pontiac Models. In all cases, an equivalent may be used.
PONTIAC DIVISION
GENERAL
MOTORS CORPORATION
PONTIAC, MICHIGAN 48053
1987 General Motors Corp. All Rights Reserved.
No part of this publication may be reproduced, stored in any
retrieval system or transmitted in any form or by any means,
including but not limited to electronic, mechanical,
photocopying, recording or otherwise, without the prior written
permission of General Motors Corp. This includes all text,
illustrations, tables and charts.
S-881 OF 9-87 Printed in Canada
TABLE OF CONTENTS
SECTION NAME
GENERAL INFORMATION
OA. General lnformation
OB. Maintenance & Lubrication
1 SECT.
HEATING AND AIR CONDITIONING
1A. Heating and Ventilation
1 B. Air Conditioning
1D1. R-4 AIC Com~ressor Overhaul
FRAME AND BUMPERS
2B. Bumpers 2C. Chassis Sheet Metal
STEERING, SUSPENSION, WHEELS
AND TIRES
3. Diagnosis
3A. Wheel Alignment
3B5. Steering Wheels and Columns 3B6. Steering Linkage 3B7. Power Steering Gear and Pump
3C. Front Suspension
3D. Rear Suspension
3E. Tires and Wheels
FINAL DRIVE
4A. Propeller Shaft
4B. Rear Axle
4B1. Bora-Warner Axle
BRAKES 5. Brakes 5A3. Comoosite Master Cvlinder 5B1. Disc r rake Caliper ~ssembly - 300013100 Series 5B6. Disc Brake Caliper Assembly - 3548
Series
5C3. Direct Torque Drum Brake Assembly 5D2. Power Head Assembly - Tandem Diaohraam 5F. ~~ecifications and Special Tools
ENGINE 6. Engine General lnformation 6A2. 2.8L 6A3. 5.OL & 5.7L 6B. Engine Cooling
6C. En~ine Fuel
6D. ~ngine Electrical 6D1. Battery 6D2. Cranking System 6D3. Charging System 6D4. Ignition System 6D5. Engine Wiring
6E. Driveabilitv and Emissions
6E2. ~missions' 6E3. Emissions - PFI
6F. Engine Exhaust
TRANSMISSION 7A. Automatic Transmission - General
lnformation
7A1. Automatic Transmission - On-Car
Service
700R4. Automatic Transmission Hydraulic Diagnosis
700R4. Automatic Transmission Unit Repair
76. 5-Speed Manual Transmission
7C. Clutch
CHASSIS ELECTRICAL 8A. Electrical Diagnosis
8B. Lighting and Horns
8C. Instrument
Panel, Gages
& Console
8E. Windshield Wiper &Washer System
ACCESSORIES 9A. Radio Systems and Antennas 9B. Cruise Control 9G. Miscellaneous Accessories
I BODY SERVICE MANUAL END
OF
MANUAL

- -
GENERAL INFORMATION OA-13
LIST OF AUTOMOTIVE ABBREVIATIONS
WHICH MAY
BE USED IN THIS MANUAL
A-6 - Axial 6 Cyl. A C Compressor AIC - Air Conditioning
ACC - Auto'matic Climate Control
EMF
- Electromotive Force PAIR - Pulse Air Injection Reaction System
EMR - Electronic Module Retard
P B - Power Brakes
EOS - Exhaust Oxygen Sensor
PCV - Positive Crankcase Ventilation
ESC - Electronic Spark Control
PECV - Power Enrichment Control Valve
APT
- Adjustable Part Throttle
AT - Automatic Transmission
ATC - Automatic Temperature Control
ATDC
- After Top Dead Center
FMVSS
- Federal Motor Vehicle Safety BAR0 - Barometric Absolute Pressure Sensor
Ft. Lb. - Foot Pounds (Torque)
Bat. + - Positive Terminal FWD - Front Wheel Drive
- Four Wheel Drive
BHP - Brake Horsepower 4 x 4 - Four Wheel Drive
BP - Back Pressure
BTDC - Before Top Dead Center
HD - Heavy Duty HE1 - High Energy Ignition
Cat. Conv. - Catalytic Converter
CC - Catalytic Converter
- Cubic Centimeter - Converter Clutch
CCC - Computer Command Control
HVM
- Heater-Vent-Module
IAC
- ldle Air Control CCOT - Cycling Clutch (Orifice) Tube IC - Integrated Circuit CCP - Controlled Canister Purge
ID - Identification
C.E. - Check Engine - Inside Diameter
CEAB - Cold Engine Airbleed ILC - Idle Load Compensator
CEMF - Counter Electromotive Force I/P - Instrument Panel
CID - Cubic Inch Displacement ISC - Idle Speed Control CLOOp - Closed Loop
CLCC - Closed Loop Carburetor Control km - Kilometers
CP
- Canister Purge kmiL - Kilometers Liter (mpg) Cu. In. - Cubic Inch kPa - Kilopascals
CV - Constant Velocity
Cyl.
- Cylinder(s)
L-4 - Four Cylinder In-Line (Engine)
DBB - Dual Bed Bead L-6 - Six Cylinder In-Line (Engine)
DBM - Dual Bed Monolith
LF - Left Front DEFl - Digital Electronic Fuel Injection LR - Left Rear DFI - Digital Fuel Injection
Diff. - Differential Man. Vac. - Manifold Vacuum Distr. - Distributor MAP - Manifold Absolute Pressure
EAC
- Electric Air Control Valve
EAS - Electric Air Switching Valve MPG - Miles Per Gallon
ECC - Electronic Comfort Control
MPH - Miles Per Hour
ECM - Electronic Control Module MT - Manual Transmission
N.m - Newton Metres (Torque)
Emission Control
Fig. 014-15 -- Common Abbreviations

MAINTENANCE AND LUBRICATION OB-1
SECTION OB
NTENANCE AND LUBR
CONTENTS
Maintenance Schedule, Gasoline .............................................. OB-l
Maintenance Schedules I and 11 .............................................. OB-2
Owner Inspections
......................................................... OB-3
Recommended Fluids and Lubricants ......................................... OB-6
PASSENGER CAR MAINTENANCE SCHEDULE
VEHICLES
WITH GASOLINE ENGINE
NORMAL CAR USE ITEM 4
The maintenance services contained in Schedules I Carburetor or Throttle Body Mounting Bolt
and 11 are based on the assumption that your car will be Torque* used as designed:
Check torque of mounting bolts and/or nuts. @ To carry passengers and cargo within the limits
shown on the Tire Placard located on the edge of the ITEM 5 driver's door.
@ On reasonable road surfaces within legal driving Engine Idle Speed Adjustment*
limits. (Engines
without Idle Speed Control or Idle Air
Control) - Adjust to specifications shown on the under- @ On unleaded gasoline.
hood label. If no specifications are shown on the label, no
adjustment is necessary. Calibrated test equipment must
EXPLANATION OF SCHEDULED MAINTENANCE be used. SERVICES
The services listed in Maintenance Scheduies I and ITEM 6
11 are further explained below. When the following main- ~i~~ and wheel aotation tenance services are performed, make sure all parts are
replaced and all necessary repairs are done before driving To equalize wear and obtain maximum tire life,
your car. Be sure to use the proper fluid and lubricants as rotate in accordance with patterns shown in Owner's
shown in Figure OB-2. Manual.
ITEM 1
Engine Oil and Oil Filter Change*
ALWAYS USE SFICC OR SF/CD ENERGY CON-
SERVING OILS OF PROPER VISCOSITY
- Also.
always change oil and filter as soon as possible after
driving in a dust storm. See your Owner's Manual for
further details.
ITEM 2
Chassis Lubrication
Lubricate all grease fittings in suspension and steer-
ing linkage. Lubricate
transmissionltransaxle shift
linkage, parking brake cable guides, underbody contact
points and linkage. Also lubricate clutch cross shaft lever
every
30,000 miles (50 000 km) on rear-wheel-drive cars
only.
ITEM 3
Carburetor Choke and Hoses*
If your car is equipped with a carburetor, verify that
choke and vacuum break work properly and are within
specifications. Correct any binding caused by damage or
gum on the choke shaft. Inspect hoses for proper hookup,
cracks, chafing or decay. Correct as necessary.
Vacuum or A.I.R. Pump Drive Belt Inspection*
When a separate belt is used to drive the vacuum or
A.I.R.
pump, inspect it for cracks, fraying, wear and
proper tension. Adjust or replace as needed.
ITEM 8
Cooling System Service*
Drain, flush and refill system with new coolant. See
your Owner's Manual
for further details.
ITEM 9
Wheel Bearing Repack (Rear-Wheel-Drive Cars
Only Except Corvette)
Clean and repack front wheel bearings at each brake
relining or 15,000 miles
(25 000 km), whichever comes
first, when car is used in such service as police, taxi or
door-to-door delivery. If you do not use your car in such
service, clean and repack bearings at each brake relining
or 30,000 miles
(50 000 km), whichever comes first.
Corvette models do not require wheel bearing repack.

OB-4 MAINTENANCE AND LUBRICATION
Tire and wheel operation - Be alert to a vibra-
tion of the steering wheel or seat at normal highway
speeds. This may mean a wheel balance is needed. Also, a
pull right or left on a straight, level road may show the
need for
a tire pressure adjustment or wheel alignment.
Steering system operation - Be alert to
changes in steering action. An inspection is needed when
the steering wheel is harder to turn or has too much free
play or if unusual sounds are noted when turning or
parking.
Headlight aim operation - Take note of light
pattern occasionally. If beam aim doesn't look right,
headlights should be adjusted.
AT EACH FUEL FILL
Engine oil level check - Check engine oil level
and add if necessary. See your Owner's
Manual for further
details.
NOTICE: A large loss in this system may indicate a
problem. Have it inspected and repaired at once.
Engine coolant level and condition - Check
engine coolant level in coolant reservoir tank and add if
necessary. Replace if dirty or rusty. See your Owner's
Manual for further details.
NOTICE: A large loss in this system may indicate a
problem. Have it inspected and repaired at once.
Windshield washer fluid level check -- Check
washer fluid level in container and add if necessary.
Hood latch operation - When opening hood on
cars equipped with hoods that open from the front, note
the operation of secondary latch. It should keep hood from
opening all the way when primary latch is released. Make
sure that hood closes firmly.
AT LEAST MONTI-ILY
Tire and wheel inspection and pressure
check--
Check tires for abnormal wear or damage. Also,
check for damaged wheels. Keep pressures as shown on
Tire Placard on the driver's door (include spare unless it is
a stowaway). Pressure should b\: checked when tires are
"cold". See "Tires" in Owner's Manual for further
infomation.
Light operation check - Check operation of
license plate light, side-marker lights, headlights includ-
ing high beams, parking lights, taillights, brake lights.
turn signals, backup lights, instrument panel and interior
lights and hazard warning flashers.
Fluid leak check - After the car has been parked
for a while, inspect the surface beneath the car for water,
oil, fuel or other fluids. Water dripping from the air
conditioning system after use is normal. If you notice fuel
leaks or fumes, the cause should be found and corrected at
once.
AT LEAST TWICE A YEAR (FOR EXAMPLE,
EVERY SPRING AND FALL)
Power steering pump fluid level check --
Check power steering pump fluid level in accordance with
Owner's Manual instructions and keep at proper level.
NOTICE: A large loss in this system may indicate a
problem. Have it inspected and repaired at once.
Brake master cylinder reservoir fluid level
check ---- Check fluid and keep at proper level. Note: It is
normal for the brake fluid level to go down slightly as the
brake pads wear
- so be sure to keep reservoir filled.
NOTICE: A large loss in this system may indicate a
problem. Have
it inspected and repaired at once.
Clutch system service --- manual transmis-
sionltransaxle --- For cars equipped with hydraulic
clutch system, check the reservoir fluid level and add fluid
as required. All others, check clutch pedal free travel and
adjust as necessary. See your Owner's Manual for further
details.
~
NOTICE: A large loss in this system may indicate a
problem. Have it inspected and repaired at once.
Weatherstrip Lubrication - Clean surface and
then apply a thin film of silicone grease with a clean cloth.
EACH TIME OIL IS CHANGED
Automatic and manual transmissionltrans-
axle fluid level check - Check transmission/transaxle
fluid level and add as required. (Corvette only) if equipped
with manual transmission
- check fluid in the overdrive
unit and add as required.
NOTICE: A large loss in this system may indicate a
problem. Have
it inspected and repaired at once.
Brake systems inspection - For convenience,
the following should be done when wheels are removed
for rotation: Inspect lines and hoses for proper hookup,
binding, leaks, cracks, chafing, etc. Inspect disc brake
pads for wear and rotors for surface condition. Also in-
spect drum brake linings for wear and cracks. Inspect
other brake parts, including drums, wheel cylinders, park-
ing brake, etc. at the same time. Check parking brake
adjustment.
INSPECT BRAKES MORE OFTEN IF DRIVING
HABITS OR CONDITIONS RESULT IN FREQUENT
BRAKING.
Steering, suspension and front drive axle
boot and seal inspection
- Inspect front and rear
suspension and steering system for damaged, loose or
missing parts, signs of wear or lack of lubrication. Inspect
power steering lines and hoses for proper hookup, bind-
ing, leaks, cracks, chafing, etc. (On cars equipped with
manual steering gear, check for seal leakage.) On
front-
wheel-drive cars, clean then inspect drive axle boot seals
for damage, tears or leakage. Replace seals if necessary.
Exhaust system inspection - Inspect complete
system. Inspect body near the exhaust system. Look for
broken, damaged, missing or out-of-position parts as well
as open seams, holes, loose connections or other condi-
tions which could cause a heat buildup in the tloor pan or
could let exhaust fumes seep into the trunk or passenger
compartment.

MAINTENANCE AND LUBRICATION OB-5
Throttle linkage inspection -- Inspect for inter-
ference, binding, damaged or missing parts.
Engine drive belts inspection - Inspect all
belts for cracks, fraying and wear. Adjust or replace as
needed.
Rear axle service (if equipped) - Check gear
lubricant level and add if needed. For cars equipped with a
limited slip rear axle, fluid does not require changing
(except Caprice and Corvette
- change fluid and required
additive at first
7,500 miles (12 500 km). See your
Owner's Manual or "Recommended Fluids
& Lubricants
Chart" in this section.
IF YOU USE YOUR GAR TO PULL A TRAILER,
CHANGE GEAR LUBRICANT EVERY 7,500 MILES
(12 500 KM).
NOTICE: A large loss in this system may indicate a
problem. Have it inspected and repaired at once.
Power antenna - Clean and then lubricate power
antenna mast. The proper lubricant as shown in Figure
OB-2 should be used.
AT LEAST ONCE A YEAR
Lap and shoulder belts condition and opera-
tion
- Inspect belt system, including webbing, buckles,
latch plates, retractors, guide loops and anchors.
Moveable head restraint operation - On cars
with moveable restraints, make sure restraints stay in the
desired position. (See adjustment instructions in your
Owner's Manual.)
Seatback latch and recliner operation on
cars equipped
with recliner seat --- Be sure seat-
backs latch on those cars with folding seats using mechan-
ical latches. Make sure the recliner is holding by pushing
and pulling on the top of the
seatback while it is reclined.
See your Owner's Manual for seat operating information.
Spare tire and jack storage- Be alert to rattles
in rear of car. Make sure the space tire, all jacking equip-
ment, any tire inflator and any covers or doors are securely
stowed at all times. Oil jack ratchet or screw mechanism
after each use.
Key lock service - Lubricate key lock cylinder at
least annually.
Body lubrication service - Lubricate all body
door hinges including the tailgate or hatchback lid (if
equipped). Also lubricate the body hood, fuel door and
rear compartment hinges and latches including interior
glove box and counsel doors, and any folding seat
hardware.
"Fansmissionltransaxle neutral or clutch
starl switch operation
CAUnON: Before pedorming the follow-
ing safety switch check, be sure to have
enough room around the car. Then, firmly
apply both the parking brake (see your
Owner's Manual for procedure) and the
regular brakes. Do not use the accelerator pedal.
If the engine
starls, be ready to turn
off the ignition promptly. Take these pre-
cautions because the car could move
without warning and possibly cause per-
sonal injury or properly damage. On auto-
matic transmissionltransaxle cars, try to
starl the engine in each gear. The starler
should crank only in "Park" or "Neutral."
On manual transmissionltransaxle cars,
place the
shiR lever in "Neutral," push the
clutch halfway and try to starl. The starler
should crank only when the clutch is fully
depressed.
Steering column lock operation
- While
parked, try to turn key to "Lock" in each gear range. The
key should turn to "Lock" only when gear is in "Park" on
automatic or "Reverse" on manual
transmissionltransax-
le. On cars with key release lever, try to turn key toULock"
without depressing the lever. The key should turn to
"Lock" only with the key lever depressed. On all vehicles,
the key should come out only in "Lock."
Parking brake and transmissionltransaxle
"Park" mechanism operation
CAUT1ON:Before checking the holding
ability of the parking brake and automatic
transmissionltransaxle "Park" mecha-
nism, park on a fairly steep hill with
enough room for movement in the down-
hill direction. To reduce the risk of person-
al injury or property damage, be prepared
to apply the regular brakes promptly if the
car begins to move.
To check the parking brake, with the engine running and
transmission/transaxle in "Neutral." slowly remove foot
pressure from the regular brake pedal (until the car is held
by only the parking brake).
To check the automatic transmissionltransaxle "Park"
mechanism holding ability, release all brakes after shift-
ing the transmissionltransaxle to "Park."
ljnderbody flushing - At least every spring,
tlush from the underbody with plain water any corrosive
materials used for ice and snow removal and dust control.
Take care to thoroughly clean any areas where mud and
other debris can collect.
Sediment packed in closed areas
of the vehicle should be loosened before being flushed.
Engine cooling system service - Inspect
coolant and freeze protection. If dirty or rusty, drain, flush
and refill with new coolant. Keep coolant
at the proper
mixture as specified in your Owner's Manual. This pro-
vides proper freeze protection. corrosion inhibitor level
and engine operating temperature. Inspect hoses and re-
place if cracked. swollen or deteriorated. Tighten hose
clamps. Clean outside of radiator and air conditioning
condensor. Wash radiator filler cap and neck.
To help
ensure proper operation. a pressure test of both the cooling
system and cap is also recommended. (See maintenance
schedule charts in Figure
OB-l for the recommended
coolant change interval.)

NOTE: Fluids and lubricants identified below by name, part number or specification may be obtained from your GM dealer.
Figure 00-2 Recommended Fluids and Lubricants
USAGE
Engine
Oil
Engine Coolant
Brake and
Hydraul~c Clutch Systems
Parking Brake Cables
Power Steering System
Manual
Steerlng Gear (reclrculat~ng ball)
Automatic
Transrn~ssionRransaxle and 5 Speed Manual Transm~ss~ons
Manual Transm~ssion (rear-wheel-drive) 4 Speed
Manual
Transm~ss~onRransaxle Shin Linkage
Key Lock Cylinders
Automatic Transmlss~onfrransaxle Shlft Llnkage
Clutch Llnkage Plvot Po~nts
Floor Sh~n L~nkage
Power Antenna Mast (3-mast sect~on-type only)
Chass~s Lubr~cation
Standard D~fferent~al Rear Axle
L~m~ted-Sl~p D~flerent~al Rear Axle
W~ndsh~eld.Washer Solvent
Hood Latch Assembly
a)
Plvots and Sprlng Anchor
b) Release Pawl
Front Wheel Bearings
(rearqwheel-drive)
Hood and door hlnges, statlon wagon tailgate hlnge or hatchback Ild and Ilnkage, headl~ght door assembl~es, statlon wagon rear foldrng seat, fuel door hlnge, rear compartment Ihd hlnges
Weatherstr~ps
FLUlDlLUBRlCANT
GM Goodwrench Motor 011 or equivalent for API Se~lce, SFICC or SFICD of the
recommended v~scos~ty
M~xture of water and good qual~ty ethylene glycol base antllreeze conforming to GM spec 1825M (GM Part No 1052753)
Delco Supreme 11
Fluld (GM Part No 1052535) or DOT-3 Fluld
Chass~s grease meetlng requirements of GM-6031M (GM Part No 1052497)
GM power
steerlng flu~d, Part No 1052884 or equivalent
Use lubricant meetlng requirements of GM-4673M (GM Part No 1052182)
DEXR0N'-II Automat~c Transm~ss~on Flu~d (GM Part No 1051855) Camaro and Flreblrd (5 Speed)
Corvette overdr~ve unlt - DEXRON a.II All others SAE-80W-90 GL-5 gear lubr~cant (GM Part No 1052271)
Chass~s grease meetlng requirements of GM-6031M (GM Part No 1052497)
Black Key Lock
Cyl~nders - light oil (GM Par1 No. 1052949)
All other Key Lock Cyl~nders - sllicone lubrlcant (GM Part No 1052277)
Eng~ne 011
Eng~ne 011
Eng~ne 011
Llght 011 (GM Part No 1052949)
Chass~s grease meetlng requirements of GM-6031M (GM Part No 1052497)
SAE
80W or SAE 80W-90 GL-5 (SAE 80W GL-5 In Canada) gear lubricant (GM Part No
1052271)
For Camaro only
- Use SAE BOW190 GL-5+ Hypold 011 (GM Part No 1050010), 11 equ~pped wl5 7L (L98) Englne or 5 OL (LB9) engine wmpeed manual transm~ss~on and disc brakes
All other applications - Use SAE 80W or SAE 80W-90 GL-5 Gear Lubr~cant (GM Part No
1052271)
GM
Opt~kleen Washer Solvent (GM Part No 1051515) or equ~valent
a) Eng~ne 011 b) Chass~s grease meet~ng requirements of GM.6031M (GM Part No 1052497)
Lubricant GM Part No 1051344 grease or equivalent
Eng~ne 011
S~l~cone Grease (GM Part No 1052863) or equivalent

AIR CONDITIONING 1B-1
SECTION 1B
R COND
When performing air conditioning diagnosis on vehicles equipped with a catalytic converter, it will be necessary to
WARM the engine to a NORMAL operating temperature BEFORE attempting to idle the engine for periods greater
than five
(5) minutes. Once the engine attains normal idle, diagnosis and adjustments can be made.
CONTENTS
.................. General Description .................................. 1B-1 Accumulator Assembly Service .1B-19
.......................... C.C.O.T. A!C System ................................ 1B-1 On-Vehicle Sewice ..... 1B-20
....................................... System Components - Functional ................. 1B-2 Blower Motor .1B-20
..................................... System Components - Control ..................... 1B-3 Hi-Blower Relay 1B-20
...................................... Relays and Switches ................................... 1B-3 Blower Resistor 1B-20
Diagnosis ................................................. 1B-5 Controller, Blower Switch or Vacuum
................................................ Testing the Refrigerant System ...................... 1B-5 Valve .lB-20
Insufficient Cooling "Quick-Check Temperature Control Cable ....................... .1B-20
.................................... Procedure.. ............................................. 1B-5 Vacuum
Harness .lB-20
C.C.O.T. A/C System Diagnostic Control Wiring Harness ........................... .1B-20
..... ................................. Procedure.. ............................................. 1B-8 Heater
Core .. .lB-21
................................ Leak Testing ........................................... 1B-12 Lower Heater Outlet 1B-21
............................... Service Procedures ................................. .1B-12 Heater Module Case .lB-21
.......................... O-Ring Replacement ................................ .1B- 12 Pressure Cycling Switch .1B-21
....................................... Handling Refrigerant- 12 ............................ .1B- 13 Vacuum Tank .lB-21
Discharging, Adding Oil, Evacuating Liquid Line .......................................... .1B-23
and
Charging Procedures - AIC Accumulator ......................................... .1B-23
.................................... Systems .............................................. .1B-14 Evaporator Core .1B-24
In-Line Air Conditioning Evaporator Case .................................... .1B-24
.......................................... Filter
Installation.. .................................. .1B- 18 Compressor .lB-24
.............................................
................ Expansion Tube (Orifice) Service .1 B- 19 Condenser IB-24
GENERAL DESCRIPTION
All engines are equipped with a fixed displace- evaporator temperature. The pressure cycling switch
ment (R-4) air conditioning compressor. This
com- is the freeze protection device in the system and
pressor may cycle on and off under normal air
senses refrigerant pressure on the suction side of the
conditioning demand. system. This switch is located on a standard
Schrader- -
All air conditioning systems that use the fixed
displacement R-4 compressor are referred to as
C. C.O.T. (Cycling Clutch, Orifice Tube) type sys-
tems. This is the same system that has been used on
all General Motors vehicles in the past several years.
The C.C.O.T. NG System
The Cycling Clutch Orifice Tube (C.C.O.T.)
refrigeration system is designed to cycle a compressor
on and off to maintain desired cooling and to prevent
evaporator freeze. Passenger compartment comfort is
maintained by the temperature lever on the controller.
Control of the refrigeration cycle (on and off
operation of the compressor) is done with a switch
which senses low-side pressure as an indicator of type
valve low-side fitting. During air temperatures
over 10°C
(50°F), the equalized pressures within the
charged
A/C system will close the contacts of the
pressure switch. When an air conditioning mode
(max, norm, bi-level, defrost) is selected, electrical
energy is supplied to the compressor clutch coil. AS
the compressor reduces the evaporator pressure
to
approximately 175 kPa (25 psi), the pressure switch
will open, de-energizing the compressor clutch.
As
the system equalizes and the pressure reaches approxl-
mately 315 kPa (46 psi), the pressure switch contacts
close, re-energizing the clutch coil. This cycling
coy
tinues and maintains average evaporator discharge air
temperature at approximately 1°C (33°F). Because of
this cycling, some slight increases and decreases of
engine speedlpower may be noticed under certain con-
ditions. This is normal as the system is designed
to
cycle to maintain desired cooling, thus preventing
evaporator freeze-up.

18-2 AIR CONDITIONING
SYSTEM GONIPONENE - FFUNCnIONAL
Compressor
All compressors are belt driven from the engine
crankshaft through the compressor clutch pulley. The
compressor pulley rotates without driving the com-
pressor shaft until an electromagnetic clutch coil is
energized. When voltage is applied to energize the
clutch coil, the clutch plate and hub assembly is
drawn rearward toward the pulley. The magnetic
force locks the clutch plate and pulley together as one
unit to drive the compressor shaft.
As the compressor shaft is driven, it compresses
the low-pressure refrigerant vapor from the evaporator
into a high-pressure, high-temperature vapor. Carried
with the refrigerant is the refrigerant oil which is used
to lubricate the compressor. Complete compressor
overhaul procedures can be found in Section
ID of the
General Service Manual.
Pressure Relief Valve
The compressor is equipped with a pressure
relief valve which is placed in the system as a safety
factor. Under certain conditions, the refrigerant on the
discharge side may exceed the designed operating
pressure. To prevent system damage, the valve is
designed to open automatically at approximately
3036
kPa (440 psi). Conditions that might cause this valve
to open (defective high pressure cut-off switch, inop-
erative electric cooling fan, etc.) should be corrected,
and the refrigerant oil and refrigerant should be
replaced as necessary.
A muffler is used on some refrigerant systems to
reduce compressor noises from high or low pressure
vibrations.
Condenser Gore
The condenser assembly in front of the radiator
is made up of coils which carry the refrigerant TO
cooling fins to provide rapid transfer of heat. The air
passing through the condenser cools the high-pressure
refrigerant vapor causing it to condense to a liquid.
Expansion (Orifice) Tube
The plastic expansion tube, with its mesh screen
and orifice, is located in the evaporator inlet pipe at
the liquid line connection. It provides a restriction to
the high-pressure liquid refrigerant in the liquid line,
metering the flow of refrigerant to the evaporator as a
low-pressure liquid. The expansion tube and orifice
are protected from contamination by filter screens on
both inlet and outlet sides. The tube is serviced only
as a replacement assembly.
When the engine is turned "OFF" with the
A/C
system operating, the refrigerant in the system will
flow from the high-pressure side of the expansion tube (orifice) to the low-pressure side until the pressure
is
equalized. This may be detected as a faint sound of
liquid flowing (hissing) for 30 to
60 seconds and is a
normal condition.
Evaporator Gore
The evaporator is a device which cools and
dehumidifies the air before it enters the car. High-
pressure liquid refrigerant flows through the expan-
sion tube (orifice) into the low-pressure area of the
evaporator. The heat in the air passing through the
evaporator core is transferred to the cooler surface of
the core, thereby cooling the air. As the process of
heat transfer from the air to the evaporator core sur-
face is taking place, any moisture (humidity) in the air
condenses on the outside surface of the evaporator
core and is drained off as water.
Accumulator
5-INTERNAL TUBE
2-REFRIGERANT 6-DESICCANT BAG
VAPOR INLET ASSEMBLY
7-FILTER ASSEMBLY
8-OIL BLEED HOLE
LOCATION IN TUBE
520004-1 8
Figure 1 Accumulator - Interior Parts
Connected to the evaporator outlet pipe, the
sealed accumulator assembly acts as a refrigerant stor-
ing container receiving vapor and some liquid and
refrigerant oil from the evaporator.
At the bottom of the accumulator is the desic-
cant which acts as a drying agent for moisture that
may have entered the system. An oil bleed hole is also
located near the bottom of the accumulator outlet pipe
to provide an oil return path to the compressor.