Thermo King UT-1200, Manual

Page: 18 / 169

Safety Precautions
18
Low Voltage
Microprocessor Service
Precautions
Take precautions to prevent electrostatic
discharge when servicing the microprocessor and
its related components. Even tiny amounts of
current can severely damage or destroy electronic
components.
Observe the following precautions when servicing
a microprocessor control system to avoid
damaging electronic components. Refer to the
appropriate microprocessor diagnostic manual for
more information.
• If the microprocessor has a power switch, turn
it OFF before connecting or disconnecting the
battery.
• Disconnect power to the unit.
• Avoid wearing clothing that generates static
electricity (wool, nylon, polyester, etc.).
• Wear a wrist strap (P/N 204-622 or its
equivalent) with the lead end connected to the
microprocessor’s ground terminal. These
straps are available from most electronic
equipment distributors. DO NOT wear these
straps with power applied to the unit.
• Avoid unnecessary contact with the electronic
components.
• Store and ship electronic components in
antistatic bags and protective packaging.
• Leave electronic components in their antistatic
packing materials until you’re ready to use
them.
• After servicing any electronic components,
check the wiring for possible errors before
restoring power to the unit.
• Never use a battery and a light bulb to test
circuits on any microprocessor-based
equipment.
Welding Precautions
Take precautions before electrically welding any
portion of the unit or the vehicle to which it is
attached. Ensure that welding currents are not
allowed to flow through the unit’s electronic
circuits.
Observe the following precautions when welding
to avoid damaging electronic components.
• If the microprocessor has a power switch, turn
it OFF before connecting or disconnecting the
battery.
• Disconnect power to the unit.
• Disconnect all wire harnesses from the
microprocessor.
• If there are any electrical circuit breakers in
the control box, switch them OFF.
• Close the control box.
WARNING: Never work alone on high
voltage circuits in the refrigeration unit.
Another person should be nearby to shut
off the unit and provide aid in the event of
an accident.
WARNING: Safety glasses, rubber-
insulated gloves and cable cutters should
be near your work area, in the event of an
electrical accident.
WARNING: Use caution when working
with electrical circuits that contain
capacitors. Some capacitors hold a
significant charge that might cause burns
or shocks if accidentally discharged. Make
sure capacitors are discharged before
working on electrical circuits.
WARNING: Control circuits used in
refrigeration units are low voltage (12 to
24 volts dc). This voltage is not dangerous,
but the large amount of amperage
available from the alternator can cause
severe burns if accidentally shorted to
ground with metal objects, such as tools.
WARNING: Do not wear jewelry, watches
or rings because they increase the risk of
shorting out electrical circuits and
damaging equipment or causing severe
burns.