1988 PONTIAC FIERO light

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

OA-2 GENERAL INFORMATION
VIN NUMBER PLATE
LOCATION
Fig. 2 Vehicle Identification Number Plate Location
marking indicating the strength of the material in the
fastener as outlined below. Metric cross recess screws
are identified by a Posidriv or Type
1A cross recess as
shown in Figure 8. Either a Phillips head or Type
1A
cross recess screwdriver can be used in Posidriv recess
screw heads, but Type
1A cross recess screwdrivers
will perform better.
NOTICE: Most metric fasteners have a blue color
coating. However, this should not be used as a
positive way of identifying as some metric fasteners
are not color coated.
General Motors Engineering Standards, along
with other North American Industries, have adopted
a portion of the standard metric fastener sizes defined
by
IS0 (International Standards Organization). This
was done to reduce the number of fastener sizes used
and yet retain the best strength qualities in each thread
size. For example, the customary 1/4-20 and 1/4-28
screws are replaced by the metric
M6.0 X 1 screw
which has nearly the same diameter and
25.4 threads
per inch. The thread pitch is in between the customary
coarse and fine thread pitches.
Metric and customary thread notation differ
slightly. The difference is shown in Figure 9.
FASTENER STRENGTH ODENTIFIGATION
Most commonly used metric fastener strength
property classes are 9.8 and 10.9 with the class
identification embossed on the head of each bolt.
Customary (inch) strength classes range from grade 2
to 8 with radial line identification embossed on each
bolt head
(i.e., grade 7 bolt will exhibit 5 embossed
radial lines on the bolt head). Some metric nuts will be
marked with single digit strength identification
numbers on the nut face. Figure 12 shows the different
strength markings.
When replacing metric fasteners, be careful to use
bolts and nuts of the same strength or greater than the
original fasteners (the same number marking or higher)
.It is also important to select replacement fasteners of
the correct size. Correct replacement bolts and nuts are
available through the parts division. Many metric
fasteners available in the after-market parts channels
were designed to metric standards of countries other
than the United States. These fasteners may be of a
lower strength, different thread pitch and may not have the
numbered head marking system. The metric
fasteners used on GM products are designed to new,
international standards that may not be used by some
nondomestic bolt and nut suppliers. In general, except
for special applications, the common sizes and pitches
are:
M 6.0
X 1
M 8 x 1.25
M 10 X 1.5 M 12 X 1.75
M 14x2 I
PREVAILING TORQUE FASTENERS
A prevailing torque nut is designed to develop an
interference between the nut and bolt threads. This is
most often accomplished by distortion of the top of an
all-metal nut or by using a nylon patch on the threads
in the middle of the hex flat.
A nylon insert may also
be used as a method of interference between nut and
bolt threads (Fig. 11).
A prevailing torque bolt is designed to develop an
interference between bolt and nut threads, or the
threads of a tapped hole. This is accomplished by
distorting some of the threads or by using a nylon patch
or adhesive (Fig. 11).
RECOMMENDATIONS FOR FASTENER REUSE: I
Clean, unrusted prevailing torque nuts and bolts
may be reused as follows:
a. Clean dirt and other foreign material off nut
or bolt.
b. Inspect nut or bolt to insure there are no
cracks, elongation, or other signs of abuse
or overtightening. (If there is any doubt,
replace with a new prevailing torque
fastener of equal or greater strength.)
c. Lightly coat bolt
& nut with engine oil.
Assemble parts and hand start nut or bolt.
d. Observe that before fastener seats, it
develops torque per the chart in Figure
10.
(If there is any doubt, replace with a new
prevailing torque fastener of equal or
greater strength.)
e. Tighten fastener to torque specified in
appropriate section of this manual.
Bolts and nuts which are rusty or damaged
should be replaced with new parts of equal or
greater strength.
VEHICLE LIF"TING PROCEDURES
NOTICE: When jacking or lifting vehicle from
frame side rails, be certain lift pads do not contact
catalytic converter as damage to converter will
result.
Many dealer service facilities and service stations
are equipped with a type of automotive hoist which
must bear upon some part of the frame in order to lift
the vehicle. Figures 14 and 15 indicate the
recommended areas for hoist contact for Pontiac
Sunbird models.
If any other hoist methods are used, special care
must be used not to damage the fuel tank, filler neck,
I
exhaust system or underbody. I

GENERAL INFORMATION OA-9
REUSE OF PREVAILING "TRQUE NUT AND BOLT
WASHER NYLON STRIP OR PATC
I
A. CLEAN, llNRUSTFD PREVAILING TORQllF BOLTS AND NL'TS MAY Bk. REUSED AS FOLL.0WS I I. CLEAN DIRT AND OTHER FORFICN MATERIAL OFF NUT AND BOLT. 2, INSPECT BOLT
AND NUT TO ASSURE THERE ARE NO CRACKS. ELONGATION OR OTHER SIGNS OF ABUSE OR OVERTIGIiTENING. LIGHTLY LUBRICATE THREADS. (IF
ANY DOUBT, REPLACE WITH NEW PREVAILING TOROLE FASTENER OF EQUAL OR
GREATER STRENGTH.)
3. ASSFMBLE PARTS AND START BOLT OR NLIT. 4. OBSERVE THAT BEFORE FASTENER SkATS. IT DEVk.LOPS PREVAILING TORQUE PER
CHART BELOW. (IF ANY DOUBT, INSTALL NliW PRFVAILIN(; TORQL'F FASTENER OF
EQUAL OR GREATER STRENGTH).
5. TIGHTEN TO TORQUE SPECIFIED IN SERVl('k MANl'AL,

F CARLINE
ITEM 10
TransmissionRransaxle Service
The manual transmission or transaxle fluid does not
require changing. (Corvette only.) Change fluid in over-
drive unit every 30,000 miles (50 000 km).
For automatic transmissions or transaxles, change
both the fluid and filter every 15,000 miles (25 000 km) if
the car is mainly driven under one or more of these
conditions:
@ In heavy city traffic where the outside temperature
regularly reaches 90°F (32°C) or higher.
@ In hilly or mountainous terrain.
@ Frequent trailer pulling.
@ Uses such as found in taxi, police car or delivery
service.
If you do not use your car under any of these condi-
tions, change both the fluid and filter every 100,000 miles
(160 000 km). See you Owner's Manual for further
details.
ITEM 11
Spark Plug Service*
Replace spark plugs with type listed in your Owner's
Manual.
ITEM 12
Spark Plug Wire Inspection*
Clean wires and inspect for burns, cracks or other dam-
age. Check the wire boot fit at distributor and at spark plugs.
Replace wires as needed.
ITEM 13
Positive Crankcase Ventilation (PCV) Valve
Inspection*
Inspect valve for proper function. Replace valve if
necessary as well as any worn, plugged or collapsed
hoses.
ITEM 14
EGR System Service*
Conduct EGR System Service as referenced in the
EGR System Chart shown in the appropriate 6E Section.
Also, refer to your GM maintenance schedule booklet for
specific applications.
ITEM 15
Air Cleaner and PCV Filter Replacement*
On 1.6 and 2.0 liter engines, replace every 50,000
miles (80 000 km). On all other engines, replace every
30,000 miles (50 000 km). Replace more often under
dusty conditions. Ask your dealer for the proper replace-
ment interval for your driving conditions.
MAINTENANCE AND LUBRICATION 08-3
ITEM 16
Engine Timing Check*
Adjust timing to underhood label specifications. If
no specifications are shown, no adjustment is needed.
ITEM 17
Fuel Tank, Cap and Lines Inspection*
Inspect fuel tank, cap and lines (including fuel rails
and injection assembly, if so equipped) for damage or
leaks. Inspect fuel cap gasket for an even filler neck
imprint or any damage. Replace parts as needed.
ITEM 18
Thermostatically Controlled Air Cleaner
Inspection*
If your car is equipped, inspect all hoses and ducts
for proper hookup. Make sure valve works properly.
OWNER INSPECTIONS AND SERVICES
Listed below are inspections and services which
should be made by either you or a qualified technician at
the intervals shown to help ensure proper safety, emission
performance and dependability of your car. Take any
problems promptly to your dealer or another qualified
technician for service advice. Whenever repairs are neces-
sary, have them completed at once. For your safety and
that of others, any safety-related parts that could have
been damaged in an accident should be inspected and all
needed repairs should be done before operating your car.
Be sure to use the proper fluids and lubricants as shown in
Figure OB-2.
WHILE OPERATING YOUR VEHICLE
Automatic transmissionltransaxle shift indi-
cator operation - Make sure the indicator points to the
gear chosen.
Horn operation - Blow the horn occasionally to
make sure it works. Check all button locations.
I
Brake system operation -- Be alert to abnormal
sounds, increased brake pedal travel or repeated pulling to
one side when braking. Also, if a brake warning light
comes on or flashes, or the anti-lock warning light (if
equipped) comes on or remains on, something may be
wrong with part of the brake system. Have it inspected and
repaired at once.
Exhaust system operation - Be alert to any
changes in the sound of the system or any smell of fumes.
These are signs the system may be leaking or overheating.
.
Have it inspected and repaired at once. Also see "Engine
Exhaust Gas Caution (Carbon Monoxide)" and "Catalytic
Converter" in your Owner's Manual.
*An Emission Control Service

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.

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

HEATING AND VENTILATION 1A-7
@ BLOWER ELECTRICAL
LOCATE SHORT IN THE
FOLLOWING WIRES:
1. FROM THE FUSE PANEL
2. FROM THE BLOWER
SPEED SWITCH TO THE
HEATER RESISTOR BLOCK.
3. FROM THE HEATER RE-
SISTOR BLOCK. CONNECT A
JUMPER LEAD FROM THE BAT-
TERY POSITIVE TERMINAL TO
ANY
WlRE TERMINAL IN THE
CONNECTOR. USE
12 VOLT
TEST LIGHT TO CHECK FOR
VOLTAGE AT THE CORRES-
PONDING WIRE ON THE
USE THE
12 VOLT
TEST LIGHT TO
CHECK THE POWER
FEED TERMINAL ON
THE BLOWER
SPEED SWITCH
TEST LAMP DOES BLOWER
SPEED SWITCH.
REPAIR OPEN IN FEED
WlRE FROM RESISTOR TO
BLOWER MOTOR.
Fig. 9 Blower Electrical Diagnosis

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.