Yale MPB045VG Maintenance Manual Download

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Electrical Test Equipment

ELECTRICAL TEST EQUIPMENT

Before beginning intrusive circuit checks, verify the
vehicle battery state of charge. Visually inspect
suspected connectors for loose, damaged, or corroded
terminals. Check for blown fuses and inspect circuits
for cause of overcurrent conditions. Physically check
mechanical operation to ensure a switch, relay, or
solenoid is not sticking or damaged.

NOTE:

Measuring continuity between two terminals of

a switch while operating the switch will determine its
functionality.

PC Service Tool

The PC Service Tool is a Windows based service
application that is used to communicate with the
truck’s electrical control system. It can be used to
monitor the status and condition of various systems.
With this capability, the PC Service Tool can be used
to monitor component operation, or determine if
abnormal events have occurred in the truck, and assist
with diagnostics and troubleshooting.

Digital Multimeter (DMM)

Digital multimeters provide several measurement
functions in one tool. A DMM should be capable of
accurately measuring voltage, amperage, and
resistance. Ensure that the multimeter used in
troubleshooting procedures is accurate and that the
test leads do not have excessive resistance. A faulty
meter or damaged test leads will cause inaccurate
readings and incorrect electrical diagnoses.

Jumper Wires, Test Leads, and Test Lights

When using jumper wires, test leads, and test lights,
take care not to force tips into connector sockets. Use

appropriate clips and adapters to prevent damage to
connectors. Expanded or damaged sockets can cause
poor continuity between connections.

Jumper wires allow testing across a suspected open in
the circuit. Jumper wires can be used for located
opens, shorts, and performing voltage drops. If a
circuit operates correctly with the jumper wire in place,
and is faulty when the jumper wire is removed, a fault
can be found in the bypassed location.

Jumper wires can also be used to eliminate sections of
the circuit to diagnose either power or grounds. Using
the jumper wire to provide a component a known good
ground can help reduce the amount of checks needed
to diagnose a circuit.

Jumper wires can be used to bypass components
such as switches. If a faulty switch is suspected,
removing it from the circuit with a jumper wire can
determine if a switch or component is at fault.

Jumper wires can be used to check for open or faulty
relay contacts which are often sealed and can take
additional steps to properly diagnose.

Test lights can be used when quick voltage or ground
checks are necessary. Many features operate on
switched voltage, and using a test light as a load
device may be helpful. The test light may also be used
to verify continuity to B-. Discretion should be used
when troubleshooting a circuit using a test light, as the
light may illuminate even though there may be an
excessive amount of resistance on the ground circuit
or when a low voltage or amperage situation exists.

Basic Electrical Troubleshooting

ELECTRICAL CHECKS

The following electrical checks are used to diagnose
circuit and component faults on trucks. Review the
following information so that it may be applied when
diagnosing a fault or status code.

Voltage Checks

Voltage is electrical pressure or force that pushes
current through a circuit. The force is measured in
volts.

Low voltage to a load device will cause the device to
be inoperative or operate poorly. This can be caused
by a low battery source, high circuit resistance, poor
connections, or an open circuit; the resistance of poor

ELECTRICAL SYSTEM

General Maintenance and Diagnostic Data

Check the Service Manual section in Yale Axcess Online for possible updates and check pertinent Bulletins

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9030-03-3