Chapter 4 Safety 75
manufacturer installs guards on all of these
devices. These guards should never be removed,
except for service operations such as changing
the grinding wheels.
Know what types of chemicals are stored on
the shop premises. Chemicals include carburetor
cleaners, hot tank solutions, parts cleaner, and
even motor oil and antifreeze. Chemical manu-
facturers provide a Material Safety Data Sheet,
often called MSDS, for every chemical that they
produce. The MSDS lists all of the known dan-
gers of the chemical, as well as fi rst aid proce-
dures for skin or respiratory system contact.
There should be an MSDS for every chemical
present in the shop. Locate the MSDS and read
it before working with any unfamiliar chemical.
Ensure that the shop is well ventilated. A
sealed shop, or a closed room in the shop, can
permit the buildup of exhaust fumes or chemi-
cal vapors, which can be fatal. Even a seemingly
harmless gas like air conditioner refrigerant can
kill if it displaces all of the oxygen in a closed
room.
Make sure that the shop is well lighted.
Poor lighting makes it hard to see what you are
doing. Not only does it make the job more time-
consuming, it can lead to accidental contact with
moving parts or hot surfaces. Overhead lights
should be bright and centrally located. Portable
trouble lights or droplights, which are usually
small and easy to use, should be used in close
operating conditions.
Always use a rough service bulb in drop-
lights. These bulbs are more rugged than nor-
mal lightbulbs and will not shatter if they are
dropped. Do not use a high wattage bulb in a
droplight. Lightbulbs get very hot and can melt
the light socket or burn anyone who touches the
light safety cover. When possible, use droplights
with light emitting diodes, or LEDs, instead of
incandescent bulbs. LED droplights do not cre-
ate heat and are less likely to break than drop-
lights that use incandescent bulbs.
Do not overload electrical outlets or exten-
sion cords by operating several electrical devices
from one outlet. Do not pair up high-current
electrical devices, or operate them through
extension cords. Examples of electrical devices
that draw high current are drills, grinders,
and electric heaters. Do not, under any circum-
stances, cut or break off the ground prong of a
three-prong plug.
Additional Precautions for Hybrid
Vehicles
Hybrid vehicles are becoming common,
and will probably make up a large percentage
of vehicles in the future. Two features of hybrid
vehicles require that the technician take special
precautions: the high-voltage electrical system
and the cooling system.
Electrical Precautions
The batteries used on hybrid vehicles pro-
duce extremely high voltages that can cause
electrocution. The technician should take the
following precautions on every hybrid vehicle
before beginning any service operations.
Warning
Do not assume that a dead high-
voltage battery is safe. A high-
voltage battery that will no longer
operate the vehicle may still produce
several hundred volts.
Begin by checking the manufacturer’s ser-
vice information for exact procedures and to
identify the vehicle’s high- and low-voltage cir-
cuits. Put on insulated rubber gloves when you
are near any of the high-voltage electrical compo-
nents. Next, locate the high-voltage components
and cables on the vehicle. High-voltage cables
on most hybrid vehicles are covered with orange
insulation for easy identification, as in Figure 4-7.
Check the vehicle service information for
the exact location of the disconnect device.
The shape and location of a typical discon-
nect is shown in Figure 4-8. On some vehicles,
removing the negative terminal clamp from the
auxiliary battery will disable the high voltage
circuits. On other vehicles, it may be necessary
to remove a clearly marked service disconnect
plug, high-voltage circuit control fuse, or control
relay specifically designed to disable the high-
voltage system.
Wait at least fi ve minutes to allow the full
discharge of the high-voltage condensers. Then
use a voltmeter or multimeter to test the high-
voltage cables for low or zero voltage. Less than
12 volts is considered safe. After repairs are com-
pleted, reinstall the applicable device to restore
high voltage to the vehicle.