The high voltage can instantly make the metal watch glow
red hot, burning deep into your wrist or arm. If a metal
necklace touches high-voltage conductors, it can weld
itself to the conductors. It will then glow red hot, begin to
melt, and may even explode in sparks of molten metal.
Wear Eye Protection
Make sure you wear safety glasses or goggles when
working on high-voltage hybrid components. If a high-
voltage cable shorts to ground, a violent electric arc will
occur. The metal end of the shorted cable will melt and
may shoot out molten metal. If the molten metal gets in
your eyes, you can suffer permanent eye injury.
Wear Insulating Gloves
Always wear thick rubber insulating gloves when
working on hybrid power cables and other hybrid com-
ponents. The high voltage in hybrid vehicles can arc
through cloth or thin rubber gloves, causing serious
injury or death. Make sure you use OSHA approved
“lineman gloves” or gloves with an approved insulation
value of 1000 volts. See Figure 38-22.
Periodically inspect your insulating gloves for tears
or splits, especially in the fingertips. To check the condi-
tion of insulating gloves, grasp a glove by the cusp and
fold it over a couple times to seal air inside the glove.
With the glove filled with air, check for air leakage and
flaws. If the glove leaks air, it can also leak voltage. If
your gloves are worn or damaged, discard them and pur-
chase new ones.
Wear Rubber-Soled Shoes
Since the voltages are so high in a hybrid, you should
wear shoes with rubber soles when working on hybrid
vehicles. Rubber soles help insulate your body from earth
ground, preventing high voltage from arcing out of the
high-voltage conductors and into your body while
seeking earth ground (conduction of electricity into the
shop floor).
Keep a Fire Extinguisher Nearby
Always keep a class A, B, C fire extinguisher near the
work area when servicing hybrids. A high-voltage elec-
trical short can cause a serious electrical fire. If fire starts,
shut off the main contactor or switch for the battery pack
and then put out the fire with a fire extinguisher.
Towing Safety
With some hybrids, spinning the wheels and axles
will cause the motor-generator to produce high voltage,
which can be dangerous and may damage the drive
system. Therefore, when towing or moving a hybrid
vehicle, the drive wheel engaged to the motor-generator
should be raised off the ground.
The front wheels of a front-wheel drive hybrid
should be raised when towing. If you are towing an all-
wheel drive hybrid with motor-generators at the front and
rear, all four wheels should be raised off the ground.
Disable the Hybrid Drive when Working
A “hot hybrid” system is one with high and low
voltage still present in the electric drive system. Although
you cannot turn off the power stored inside the battery
pack, you can disconnect it from the rest of the hybrid
drive system.
To disable a gas-electric hybrid for repair, you must
first turn the ignition key off. This will cause the hybrid
ECU to de-energize the relays that connect the battery
pack to the rest of the system. Some automakers also
require that you disconnect the conventional 12-volt bat-
tery to help prevent the high-voltage circuits from acci-
dentally being energized.
Disabling the system is important because a hybrid’s
drive train may be engaged and ready to accelerate even
without the internal-combustion engine running. If you
leave the key on in a hybrid and the shift lever is in gear
(drive or reverse), the vehicle can be propelled forward or
710 Section 5 Electrical Systems
Figure 38-22. Learn to respect the power of a hybrid electric
drive system. A—Wear thick rubber gloves to help insulate your
body from the high voltages in a hybrid drive. (Toyota)