This sample chapter is for review purposes only. Copyright © The Goodheart-Willcox Co., Inc. All rights reserved.
Chapter
5
Shop Safety
After studying this chapter, you will be able to:
K List common types of accidents.
K Identify fire hazards.
K Explain how an electrical fire can start.
K Identify asphyxiation hazards.
K List safety rules.
K Explain what qualifies a material as a hazardous waste.
K Describe the regulations concerning the disposal of hazardous wastes.
K Explain the importance of material safety data sheets.
Know These Terms
Asphyxiation
Ignitable hazard
Corrosive hazard
Material safety data sheet
(MSDS)
Electrical fires
Reactivity hazard
Explosion
Respirators
Fire
Toxicity hazard
Gasoline
Hazardous waste
111
112
Auto Engine Repair
Hundreds of engine technicians are injured or killed
each year while on the job. A majority of these incidents
resulted from broken safety rules, Figure 5-1. As an engine
technician, you will be exposed to many potentially
dangerous situations. You will be working around running
engines, engines suspended in the air on a hoist, gasoline,
and numerous other possible hazards. Moving vehicles in
the close quarters of a service facility can also be hazardous.
You must learn to control these dangerous situations and
keep your job safe and enjoyable. This chapter reviews
basic shop safety and will help you gain basic safety skills.
Types of Accidents
There are six common types of accidents—fires,
explosions, asphyxiation, chemical burns, electric shock,
and physical injuries. To create a safe working environment, you must prevent these. Each could cripple or kill
you or someone else.
Fires
A fire can cause horrible destruction, injury, and
death. Fire is the result of heat, fuel, and oxygen in the correct proportions to start combustion. When working on
engines, gasoline, diesel fuel, cleaning solvents, and oily
rags are just a few of the many possible sources of fuel in
a service facility. Fire extinguishers are rated in terms of the
type of fire for which they should be used. See Figure 5-2.
Gasoline is the most dangerous flammable in the
shop, Figure 5-3. Just a cup of ignited gasoline can engulf
a whole engine compartment in flames. The fire may then
consume the rest of the vehicle and maybe the entire shop.
A few rules for handling gasoline include:
K Never use gasoline as a cleaning agent. Cleaning solvents are flammable, but not as flammable as gasoline.
K Keep sources of heat, such as welding and cutting
equipment, away from the engine’s fuel system.
K Wipe up gasoline spills right away. Do not spread oil
absorbent (oil-dry) on a gasoline spill because the
absorbent will become flammable.
K Disconnect the car battery before working on the fuel
system.
K Wrap a shop towel around any fitting when disconnecting a fuel line. This will collect fuel that leaks or
sprays out.
K Store gasoline and other flammables in approved,
sealed containers.
Electrical fires can occur when a current-carrying
wire shorts to ground. This causes unlimited current flow,
which in turn causes the wire to heat up, melt its insulation, and burn. See Figure 5-4. Then, other wires may short
and burn. In this repeating pattern, the wiring through
much of the car can quickly begin to burn.
To prevent electrical fires, disconnect the car battery
before working on any wiring. Since there is no power
source connected, you cannot accidentally create a short.
Explosions
An explosion is a violent expansion of gasses due to
rapid combustion. There are several possible sources of
explosion when servicing an engine or its systems. For
example, a vehicle’s battery can explode. The chemical
reaction that takes place inside of the battery to produce
electricity also generates hydrogen gas. As shown in
Figure 5-5, this highly explosive gas can surround the top
of the battery. The slightest spark or flame can ignite the
gas and cause the battery to explode. Fragments of battery
case and the battery acid can travel through the air as the
result of the explosion. Blindness, cuts, acid burns, and
scars can result.
Various other sources can result in explosions. For
example, sodium-filled engine valves, welding tanks,
propane bottles, and fuel tanks can all explode if mishandled. These hazards are discussed in later chapters
where appropriate.
Asphyxiation
Figure 5-1. A running engine can be dangerous. Hot parts can
cause burns. Spinning fans can cause deep cuts. Exhaust
fumes can cause asphyxiation.
Asphyxiation is a condition in which the body has too
little oxygen or too much carbon dioxide. It may be caused
by breathing toxic or poisonous substances in the air. Mild
cases of asphyxiation will cause dizziness, headaches, and
vomiting. Severe asphyxiation can cause death.
The most likely source of asphyxiation in a service facility is the exhaust gasses from the vehicle’s engine. Exhaust
contains very little oxygen. Coupled with the fact that the
engine is consuming oxygen for combustion, the oxygen in an
enclosed shop can quickly be depleted. In addition, an
engine’s exhaust gasses contain carbon monoxide, which is
deadly poison. Using an exhaust hose, connect the vehicle’s
tailpipe to the shop’s exhaust ventilation system, Figure 5-6.
Chapter 5
Shop Safety
113
Fire Extinguishers and Fire Classifications
Fires
Type
Use
Class A Fires
Ordinary Combustibles
(Materials such as wood,
paper, textiles.)
Requires...
cooling-quenching
Soda-acid
Bicarbonate of
soda solution
and sulfuric
acid
Okay for use on
Old
B
Pressurized Water
Water under
pressure
Class B Fires
Flammable Liquids
(Liquids such as grease,
gasoline, oils, and
paints.)
Requires...blanketing or
smothering.
Old
A
New
D
C
Okay for use on
A
Direct stream at base of
flame.
Not for use on
B
Carbon Dioxide (CO2)
Carbon dioxide
(CO2) gas
under pressure
C
D
Okay for use on
B
Direct discharge as
close to fire as possible,
first at edge of flames
and gradually forward
and upward.
C
Not for use on
B
D
A
Class C Fires
Electrical Equipment
(Motors, switches, and so
forth.)
Requires...
a nonconducting agent.
Old
Direct stream at base of
flame.
Not for use on
New
A
Operation
Foam
Solution of
aluminum
sulfate and
bicarbonate
of soda
Okay for use on
Not for use on
C
New
C
Class D Fires
Combustible Metals
(Flammable metals such
as magnesium and
lithium.)
Requires...blanketing or
smothering.
Dry
Chemical
D
Multi-purpose
type
Ordinary BC
type
Okay for
Okay for
B
A
B
C
Not okay for
C
A
D
Okay for use on
Smother flames by
scooping granular
material from bucket
onto burning metal.
D
D
Direct stream at base of
flames. Use rapid leftto-right motion toward
flames.
Not okay for
D
Dry Chemical
Granular type material
Direct stream into the
burning material or
liquid. Allow foam to
fall lightly on fire.
B
A
Not for use on
A
B
C
Figure 5-2. There are different types of fires. Fire extinguishers are rated by the type of fire on which they should be used.
Also, make sure the exhaust ventilation system is turned on
whenever the engine is running.
There are other substances in the shop that are harmful if inhaled. One of these harmful substances is asbestos,
which may be found in the dust from a clutch disc or
older brake pads. Respirators (filter masks) should be
worn when working around any kind of airborne impurities, Figure 5-7. If welding during major engine repair or
in a machine shop, a special welding respirator should be
worn. It will trap toxic welding fumes and block them
from entering your nose, mouth, throat, and lungs.
Warning: A filter mask or respirator will
only protect you from the substances for
which it is rated. A dust mask will not protect against toxic fumes.
114
Auto Engine Repair
Hydrogen gas
plus spark equals
battery explosion
Figure 5-3. Gasoline is the most dangerous and underestimated
flammable. A cup of gasoline, when ignited, can engulf a
vehicle in flames.
Figure 5-5. A battery can explode, caused by a spark igniting
the hydrogen gas that can collect around the top of the battery.
Chemical Burns
Various solvents, battery acid, and a few other substances
found in the shop can cause chemical burns to the skin.
Decarbonizing cleaner (“carb cleaner”), for example, is powerful and can severely burn your skin in a matter of seconds.
Always read the directions and warnings on chemicals. See
Figure 5-8. Wear rubber gloves and eye protection. If a skin burn
occurs, follow the treatment directions on the product label.
Shop Safety
115
Figure 5-7. When working around airborne toxins, wear an approved
respirator. It will help keep harmful chemicals out of your lungs.
current from accidentally passing through your body. Also,
never use an electric tool on a wet shop floor.
Figure 5-8. Battery acid can cause severe chemical burns.
Make sure you read and follow label directions on caustic products. Note the treatments (antidotes).
Warning: Use extreme caution when working with hybrid vehicles. They operate at
voltages as high as 600 volts AC. This is
enough electricity to kill.
required. For example, why move an engine block by hand
when a crane is available? You and a friend may be strong
enough to lift the engine block, but why risk back injury?
Once your back is injured, it will never be the same!
General Safety Rules
Physical Injury
Physical injuries, such as cuts, broken bones, and
strained backs, can result from hundreds of different accidents. As an engine technician, you must constantly think
and evaluate every repair technique. Decide whether a
particular operation is safe or dangerous and take action as
Electric Shock
Electric shock can occur when using improperly
grounded electric power tools. Never use an electric tool
unless it has a functional ground prong. This is the third,
round prong on the plug. The ground prong prevents
Chapter 5
The following list provides several general safety
rules. Remember these and follow them at all times.
K Wear appropriate eye protection during any operation
that could endanger your eyes! See Figure 5-9. This
includes operating power tools, working around a
Exhaust
hose
Figure 5-6. Use an exhaust ventilation system when running an
engine in an enclosed area.
Electrical fire
burns insulation
Load shorted
out of circuit
Safety Glasses
Safety Goggles
Full Face Shield
Tinted Safety Glasses
Welding Goggles
Welding Helmet
No load causes
excess current
Hot wires
touch ground
Figure 5-4. Electrical fire can occur when a wire shorts to ground. The resulting high current causes enough heat to make the wire
insulation burn. Always disconnect the battery before working on wiring.
Figure 5-9. Wear appropriate eye protection. There are several types available for different situations.
116
K
K
K
K
K
K
K
K
K
K
K
Auto Engine Repair
spinning engine fan, carrying batteries, using a cutting
torch, and welding.
Keep your shop organized. Return all tools and equipment to their proper storage areas. Never lay tools or
parts on the floor, Figure 5-10.
Dress like a professional technician. Remove rings,
bracelets, necklaces, watches, and other jewelry.
They can get caught in engine fans, belts, etc., causing injury. Also, roll up long sleeves and secure long
hair. They, too, can get caught in spinning parts.
Work like a professional. When learning to be an
engine technician, it is easy to get excited about your
work. However, avoid working too fast. You could
overlook a repair procedure or safety rule and cause
an accident.
Use the right tool for the job. There is usually a tool
that is best suited for each repair task. Always ask
yourself this question: Is there another tool that will
work better?
Never carry sharp tools or parts in your pockets. They
can easily puncture your skin.
Keep equipment guards or shields in place. If a power
tool has a safety guard, use it. Refer to Figure 5-11.
Lift heavy parts with your legs, not with your back.
When lifting, bend at your knees while keeping your
back as straight as possible. On extremely heavy
assemblies, such as transmissions, engine blocks, and
transaxles, use a portable crane.
Use adequate lighting. A portable shop light increases
safety, work speed, and precision.
Ventilate your work area when needed. Turn on the
shop ventilation fan or open the shop doors anytime
fumes are present in the shop.
Never stir up asbestos dust. Asbestos is a cancer-causing
agent. Do not use compressed air to blow the dust off
brake parts or clutch assemblies.
Jack up or raise a vehicle slowly and safely, Figure 5-12.
A car or light truck may weigh as much as two tons.
Figure 5-10. Always keep tools organized while working. Do
not lay tools on the floor. This roll around cart can be used to
hold all tools needed for the job. (Snap-on Tool Corp.)
Light
Chapter 5
Shop Safety
117
Shield
A
A
Tool rest
Leather
gloves
Figure 5-11. Always use a protection device when needed.
Here, the tool rest is being used to hold and secure a chisel
while sharpening.
Wheel
chock
K Never work under a vehicle unless it is supported by jack
stands, Figure 5-13. It is not safe to work under a vehicle
held up by only a floor jack. Also, chock (block) the
vehicle’s wheels when the car is on jack stands.
K Drive slowly when in the shop area. With students and
vehicles in the shop, it is very easy to have an accident.
K Keep away from spinning engine fans. The engine fan
is like a spinning knife. It can inflict serious injuries.
Also, if a part or tool is dropped into the fan, it can fly
out and hit someone or damage the radiator.
K Respect running engines. When an engine is running,
make sure that the transmission or transaxle is in park.
Check that the emergency brake is set and that the
wheels are blocked.
K Do not smoke in the shop. Smoking is a serious fire
hazard considering fuel, cleaning solvents, and other
flammables that are in the shop.
K Chemical pneumonia can result from inhaling oil
mist. Dermatitis can result from skin contact with oil.
Figure 5-12. Stay out from under vehicle as it is being raised or
lowered. Also, raise and lower the vehicle slowly.
B
B
Figure 5-13. A—Jack stands must be used while working under
vehicle. It is not safe to work under vehicle held only by a floor
jack. B—Chock (block) the wheels when the vehicle is lifted to
keep the vehicle from rolling off the jack stands. (Subaru)
K Obtain permission before using any new or unfamiliar
power tool, lift, or shop equipment. Your instructor will
need to provide training on proper use. See Figure 5-14.
K Wear ear protection when using loud power tools. For
example, if you are using an air chisel to cut off an old
exhaust system, the sound generated by the hammer action
can be above a safe limit. To avoid partial loss of your hearing, wear earplugs or earmuffs, as shown in Figure 5-15.
K Wear gloves when needed while working. Leather
gloves will protect your hands from cuts and abrasions. Latex or rubber gloves can be used to protect
your skin from oil and grease.
K Use compressed air with caution. Air lines can contain
up to 150 psi (1000 kPa) of air pressure. If air is forced
through your skin and into the bloodstream, death can
result. Never direct a blow nozzle at you or anyone else.
K Many air tools have a pressure regulating valve to limit
tool speed or power, Figure 5-16. Always adjust the pressure control to the lowest-possible setting that will do the
job. This will help avoid part damage and possible injury.
K A clean shop is a safe shop. Always do your part to
keep the service facility clean and organized. See
Figure 5-17. A cluttered, disorganized shop indicates
a very disorganized technician.
K Report unsafe conditions to your instructor. If you
notice a hazard, inform your instructor immediately.
K Avoid anyone who does not take shop work seriously.
K If an accident or injury ever occurs in the shop, notify
your instructor immediately.
Figure 5-14. A—Never use equipment for which you are not
trained. This technician has been instructed in the proper locations for the lift arms. B—Since the technician that placed the
vehicle on the lift was properly trained, the vehicle is secure and
work can be safely completed under the vehicle.
Figure 5-15. Wear ear protection in loud or noisy situations.
(Snap-on Tool Corp.)
Lift Safety
Safety is always important, but especially so when using
floor jacks and vehicle lifts. A vehicle can weigh 3000 lbs
(1360 kg) or more. The careless use of lift equipment results in
numerous injuries and deaths each year. In addition to bodily
harm, equipment and customer vehicles are damaged.
Before using any type of shop equipment, lifts and jacks
included, learn the proper procedure for using the equipment. Respect the dangers that the equipment presents.
Follow all safety rules and learn to “think before you act.”
118
Auto Engine Repair
K Securely engage the lift safety lock before working
under the vehicle.
K Do not change the working height of the lift unless all
personnel are out from under the vehicle.
K When using a floor jack, always place jack stands
under the vehicle before working on the vehicle.
K Always check for equipment, parts, and personnel
under the vehicle before lowering it.
K Lower a vehicle slowly. Watch the vehicle and lift
closely until the lift is fully lowered and the vehicle is
firmly on the ground.
Figure 5-16. Many air tools, like this air impact wrench, have a
power or speed adjustment knob. Set the tool for the lowest possible pressure needed to complete the task. (Snap-on Tool Corp.)
Disposing of Shop Wastes
Automotive service and maintenance facilities
frequently generate hazardous wastes. These wastes are
regulated by the Resource Conservation and Recovery Act.
This federal act applies to businesses that generate, transport, or manage hazardous wastes. Any business that
maintains or repairs vehicles, heavy equipment, or farm
equipment must comply with the regulations of the act.
Hazardous Waste
Figure 5-17. These technicians are cleaning up outside their
shop. Doing so increases shop safety, but it also makes the
shop appear more professional to customers.
In addition to following safe operating procedures, the
equipment must be in good operating condition to perform
safely. Do not use equipment that has cracked or bent parts,
faulty safety locks, leaking cylinders, or other problems.
Study the following safety precautions carefully. They
apply to all types of lifting equipment.
K Before lifting any vehicle, determine how the weight
is distributed on the vehicle. For example, a frontwheel drive vehicle is heavier at the front of the vehicle
than a rear-wheel drive vehicle because of the
transaxle. Therefore, the lift saddles at the front of the
vehicle must be positioned to account for this.
K Position the lift saddles so they securely contact the
vehicle’s chassis. Most vehicles have certain lift points
designed into the frame or unitized body.
K With saddles properly positioned, raise the vehicle
until its weight is fully supported by the lift (wheels
are just off the ground). Then, carefully push down on
one end of the vehicle. If the vehicle moves on the
saddles or feels unstable, lower the vehicle and
reposition the saddles before proceeding.
K When raising a vehicle, watch for side or overhead
obstructions.
Hazardous waste is a solid, liquid, or gas that can
harm people or the environment. There are several criteria
for determining if a substance is hazardous.
A material is considered an ignitable hazard if it will
easily ignite and burn. Gasoline, diesel oil, solvents, and
other chemicals are considered ignitable hazards.
A material or waste is a corrosive hazard if it dissolves
metals and other materials or burns human skin. Battery
acid and many part-cleaning solvents are considered
corrosive hazards.
Anything that reacts violently or releases poisonous
gasses when in contact with other materials is considered a
reactivity hazard. Materials that generate toxic mists, fumes,
vapors, and flammable gasses are also reactive hazards.
Materials like lead, cadmium, chromium, arsenic,
and other heavy metals that can pollute and make water
and soil harmful are considered a toxicity hazard. Used
motor oil, solvents, and other chemicals in the auto shop
are toxic hazards that must be disposed of properly.
Chapter 5
K
K
K
K
Shop Safety
Old batteries. These contain lead and toxic chemicals.
Old tires and catalytic converters.
Antifreeze.
Refrigerant.
Recycling Motor Oil
Used motor oil should be recycled. One gallon of
used motor oil can be recycled into two and one-half
quarts of high-quality motor oil. Recycling old oil not only
saves our environment from pollution, it helps conserve
natural resources.
Always send used oil to a recycling center. The old oil
should be stored in an approved container and kept
separate from other fluids. Some recycling companies
provide a pickup service, while others require you to take
the old oil to their facility.
Note: As a facility that works with motor oil,
you are required to accept used oil from the
public, even if they are not a customer.
Antifreeze
Antifreeze is classified as a hazardous waste due in
part to the heavy metal and chlorinated solvents that it
picks up when circulating through an engine’s cooling
system. In addition, antifreeze presents several health
hazards. See Figure 5-18. Used antifreeze should never be
mixed with used oil. In addition, it must be collected and
disposed of by a registered hazardous waste recycling/
disposal company.
Refrigerant
The refrigerant in the air conditioning systems must
not be vented to the atmosphere. Regulations require that
they be recovered and recycled. Several types of refrigerantrecovery systems are available.
Hazardous Automotive Waste
Draining automotive fluids and replacing nonrepairable
components are the most common automotive repair activities
that produce hazardous wastes. Some automotive fluids and
solid wastes that are considered hazardous include:
K Used motor oil. It is combustible and may contain
toxic chemicals.
K Other discarded lubricants, such as transmission and
differential fluids. These may contain toxic chemicals.
K Used parts cleaners and degreasers. These are combustible and may contain toxic chemicals.
K Decarbonizing cleaners. These contain flammable or
combustible liquids.
119
Disposal
One of the best ways to deal with hazardous wastes is to
minimize the quantity produced. This can be accomplished by
practicing good housekeeping, improving inventory control,
and following proper spill-containment techniques.
When hazardous wastes are produced, they must be
disposed of properly. Regulations require that these wastes
be collected by a registered hazardous waste hauler.
Several major companies offer pick up and recycling
services. Repair or maintenance facilities that generate
220 lb (100 kg) of hazardous waste monthly must fill out a
Uniform Hazardous Waste Manifest before shipping the
wastes to a disposal or recycling site. The manifest is
simply a tracking document that must accompany
hazardous wastes when they are shipped from the work
facility. It contains detailed information about the origin,
character, and destination of the wastes. When shipping
certain wastes, the proper Department of Transportation
(DOT) shipping descriptions must be listed on the
manifest. Tables listing these descriptions are available
from each state’s hazardous waste management agency or
from a regional EPA office.
EPA regulations state that no manifest is needed for
used oil or lead-acid batteries sent off for recycling. In such
cases, the material is not regarded as hazardous. Your state
might have its own requirements. Check with your state
hazardous waste management agency.
Used oil filters are considered hazardous waste unless
they are to be recycled for scrap metal. If not recycled,
they must be listed on the manifest as hazardous. Before
disposal, oil filters should be gravity drained so that they
do not contain free-flowing oil. Then, store them in a
closed, labeled container for pickup by a recycler.
Material Safety Data Sheets
Always read label directions when using chemicals.
Rust penetrant, lubricants, part cleaners, and other
substances can be dangerous if not used properly. The
product label will give general precautions for using the
product, Figure 5-19. Further information can be obtained
from the product’s material data safety sheet.
Chemical manufacturers are required to provide a
material safety data sheet (MSDS) for each chemical that
they produce. This sheet is important because it lists all of
the known dangers and treatment procedures for a specific
chemical. Employers are required to have an MSDS for
each chemical or substance used in their facility. Be sure
to read the MSDS for any chemical or substance that you
are not familiar with.
Hybrid Service Safety
Figure 5-18. Antifreeze and other shop substances are
poisonous. These substances should be stored in a location
where children and animals cannot get to them. The warning
label will provide treatment recommendations.
A hybrid vehicle uses a gasoline engine, a powerful
motor-generator, and a battery pack to propel the vehicle.
Hybrid vehicles have specific safety recommendations that
120
Auto Engine Repair
Hybrid Voltage
Modern gas-electric hybrid drive systems have
enough electrical energy to cause electrocution. Most
hybrid vehicles conduct 3-phase AC at almost 600 volts
and almost 300 volts DC at hundreds of amps. By comparison, the voltage at a home wall outlet is 120 volts AC. Yet
many people are killed or injured each year by that voltage.
The 240 AC fed into a repair shop operates high-power equipment (air compressors, central air conditioning, furnaces, vehicle lifts, etc.). If shorted to ground, 240 volts causes a powerful
electric arc. Since hybrids operate at even higher voltage levels, it is important to respect the potential for electric shock.
Remove all jewelry when working on a hybrid’s highvoltage circuits. If metal objects come near or touch a source
of high voltage, serious burns or electrical shock can result.
Figure 5-19. Always read label directions before using any
shop chemical.
must be followed during servicing. Always determine
whether or not a vehicle is a hybrid before servicing its
engine. Look for badging on the front fender, engine cover,
or hood. The power control module, if in the engine compartment, is normally labeled and will have large orange
power cables going to it, Figure 5-20.
Towing Hybrids
When towing a hybrid vehicle, the drive wheel
engaged to the motor-generator should be raised off the
ground. This is because, on some hybrids, spinning the
wheels and axles can cause the motor-generator to produce high voltage, which can be both dangerous and damaging to the drive system. Front-wheel drive hybrids
should have the front wheels raised off the ground. Allwheel drive hybrids should have all four wheels raised.
Engine
Hybrid power control module
High voltage cables
Figure 5-20. Hybrid vehicles normally have badging on the
body or in the engine compartment. This hybrid identifies the
hybrid power control module on one side of the engine. (Toyota
Motor Company)
Clothing
Wear thick rubber gloves rated for 1000 volts when
working on hybrid high-voltage cables and other high-voltage components. Such gloves, called lineman gloves, will
insulate your body from high voltages. Periodically inspect
your gloves for tears or splits, especially in the fingertips.
Leaking, worn, or otherwise damaged gloves should be
thrown away and replaced by new gloves.
Wear safety glasses or goggles when working on
hybrids. In the instance of a short to ground, a violent electric arc will result. The metal end of the shorted cable will
vaporize, shooting out molten metal. If this metal gets in
your eyes, you can suffer serious eye injuries.
Wear rubber-soled shoes when working on hybrids.
Rubber soles will insulate your body from earth ground
(conduction of electricity into shop floor).
Chapter 5
High-Voltage Disconnect
The high-voltage disconnect provided on gas/electric
hybrids disconnects the battery pack from the power
121
control module. On some hybrids, the disconnect is pulled
out to produce an open circuit between the battery pack
and the power control module. With other designs, the disconnect has a switch that is rotated to provide an open in
the battery pack circuit.
Hybrid high-voltage disconnects are usually located near
the battery pack in the trunk, under the seat, on the side of a
seat under a trim panel, or other similar location, Figure 5-21.
Warning: In order to avoid electric shock, wait
at least five minutes after removing the hybrid
power disconnect plug before working on high
voltage circuits. It can take up to five minutes for HV
capacitors in the inverter circuit to discharge fully.
High-Voltage Buffer Zone
When working on a hybrid, set up a high voltage buffer
zone of about three feet (one meter) around the perimeter of
the vehicle. Keep steel workbenches, large metal equipment,
or any other potential conductor of electricity away from the
vehicle while working. This buffer zone helps you avoid
touching high voltage and any conductor with your body.
Service plug
Disabling Hybrid Drive
A hot hybrid system is one in which high and low
voltage are potentially present in the electric drive system.
You cannot turn off the power inside the battery pack, but
you can disconnect it from the rest of the drive system.
To disable a gas-electric hybrid for repair, turn the
ignition key off. This will cause the hybrid ECU to de-energize the relays or contactors that connect the battery pack
to the system. The ECU then verifies the relays or contactors are open, preventing current flow from the battery
pack to the motor-generator. Some automakers also require
disconnection of the conventional 12V battery, to prevent
accidental energizing of the high-voltage circuits.
System de-energization is important because a hybrid’s
drive train can be engaged and ready to accelerate even without the gas engine running. If the key is in the on position, the
vehicle can accelerate and drive forward or backward if the
gas pedal is pressed accidentally. Such movement could result
in personal injury and property damage.
Shop Safety
Summary
A service facility can be a safe and enjoyable place to
work if safety rules are followed. However, if safety regulations are not followed, the shop can be a very dangerous
place to work. Always make sure you are using approved,
safe practices when working on a vehicle.
You must prevent fires, explosions, chemical burns, electric shocks, and other physical injuries. Constantly think about
what you are doing and take corrective action when needed.
Hazardous wastes are often generated in the service facility.
These wastes are regulated by the Resource Conservation and
Recovery Act and must be disposed of properly. A material data
safety sheet provides information about a chemical or substance,
such as common reactions and treatments for overexposure.
Hybrid vehicles generate extreme electrical energy.
Therefore, specific safety rules have been developed that
must be followed during servicing. These rules address
how to tow the vehicle, how to disconnect power supplies,
and what clothing to wear to increase safety.
A
B
Service plug
Glove
C
Figure 5-21. Hybrid power disconnects can be difficult to locate. A—This disconnect plug is located in the trunk of the vehicle.
B—Here you must rotate a locking switch before you can remove the fuse disconnect. C—This disconnect plug is located on the
side of the rear seat, under a piece of plastic trim. (Ford and Toyota)
122
Auto Engine Repair
Review Questions—Chapter 5
Please do not write in this text. Write your answers on
a separate sheet of paper.
1. List six common types of accidents.
2. _____ is the most dangerous flammable in the shop.
3. Which of the following is not an acceptable cleaning agent?
(A) Decarbonizing cleaner.
(B) Gasoline.
(C) Soap.
(D) Degreasing solvent.
4. What should you do when disconnecting an engine
fuel line to prevent fuel from spaying out?
5. How can a short cause an electrical fire?
6. Batteries generate _____, which can explode.
7. Why is engine exhaust dangerous?
8. Why is a ground prong provided on electrical equipment?
9. Why should you remove jewelry when on the job?
10. Why must the drive wheel engaged to the motor-generator be raised off the ground while towing?
11. In a _____ hybrid system, high and low voltage are
potentially present in the electric drive system.
ASE-Type Questions—Chapter 5
1. Technician A says that you should disconnect the battery
before removing a fuel line from an engine. Technician
B says that you should wrap a shop towel around the
fitting before disconnecting a fuel line. Who is correct?
(A) A only.
(B) B only.
(C) Both A and B.
(D) Neither A nor B.
2. Technician A says that a fire extinguisher bearing this
symbol can be used on burning oil or gasoline.
Technician B says that a fire extinguisher bearing this
symbol can be used on an electrical fire. Who is correct?
(A) A only.
(B) B only.
(C) Both A and B.
(D) Neither A nor B.
3. The most likely source of asphyxiation in an auto
shop is _____.
(A) gasoline
(B) oily shop rags
(C) engine exhaust
(D) None of the above.
4. Technician A says that a battery can produce gasses
that can cause an explosion. Technician B says that
sodium-filled engine valves, if mishandled, can cause
an explosion. Who is correct?
(A) A only.
(B) B only.
(C) Both A and B.
(D) Neither A nor B.
5. Technician A says that a respirator will block all poisonous fumes that can be produced in a shop.
Technician B says that a respirator will block only
those fumes for which it is rated. Who is correct?
(A) A only.
(B) B only.
(C) Both A and B.
(D) Neither A nor B.
6. Technician A says that battery acid can cause chemical burns to the skin. Technician B says that some
decarbonizing cleaners can cause chemical burns to
the skin. Who is correct?
(A) A only.
(B) B only.
(C) Both A and B.
(D) Neither A nor B.
7. Technician A says that an electric power tool with a
faulty ground prong can cause electrocution. Technician B
says that if a power tool’s faulty ground prong is
removed, the power tool is safe to use. Who is correct?
(A) A only.
(B) B only.
(C) Both A and B.
(D) Neither A nor B.
8. Technician A says that eye protection should be worn
when carrying a battery. Technician B says that eye
protection should be worn when working around an
engine fan. Who is correct?
(A) A only.
(B) B only.
(C) Both A and B.
(D) Neither A nor B.
9. Technician A says that used batteries are considered a hazardous waste. Technician B says that used decarbonizing
cleaner is considered a hazardous waste. Who is correct?
(A) A only.
(B) B only.
(C) Both A and B.
(D) Neither A nor B.
10. All of the following are safety rules to follow when
working in an auto shop except:
(A) never carry sharp parts or tools in your pocket.
(B) always lift heavy engine parts with your back, not
with your legs.
(C) keep the auto shop organized.
(D) always keep equipment guards or shields in place.
11. Technician A says that refrigerants can be vented into
the atmosphere as long as proper filtering systems are
utilized. Technician B says that used motor oil should
be recycled. Who is correct?
(A) A only.
(B) B only.
(C) Both A and B.
(D) Neither A nor B.