Manitowoc National Crane NBT30H-2, Service Manual

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ELECTRIC SYSTEM NBT30H-2 SERVICE MANUAL
3-2
03-20-2019 Control # 613-06
2. Because the system used on this machine is a negative
ground system, current flows from the positive battery
terminal and returns to the negative battery terminal.
3. In series circuit arrangements, the voltage is completely
used in the circuit when the current is flowing. In parallel
circuit arrangements, the voltage is constant.
4. When the voltage is constant, resistance controls the
rate of current (amps) in the circuit. Refer to Ohm’s Law.
Comparing Electrical System to a Hydraulic
System
The electrical system is in many ways similar to a hydraulic
system. Both systems need a “pump” to cause the flow
which generates the energy. Each system needs a complete
circuit so the flow can return to storage or supply. Both
systems need “valves” to control the flow through the
system. See Table 3-1.
General Maintenance Introduction
Electrical system maintenance includes troubleshooting and
replacement of damaged components. Observe standard
wiring practices when replacing components.
General Troubleshooting
Make voltage checks at terminations when components are
installed and operating. Make continuity checks when
components are isolated or removed. Troubleshoot per the
following guidelines:
1. First, use reported symptoms to identify a problem or a
suspect component.
2. Using a multimeter, test the circuit for continuity if you
suspect a broken circuit or for voltage if you suspect a
power problem. Check the electrical schematic and
wiring diagram for most accurate wiring information.
3. If the component proves faulty, replace it with a known
working component. If wiring proves faulty, replace it
with wiring of equal gauge.
4. After troubleshooting, test and repair the repaired circuit.
Verify the circuit works properly.
Connector Troubleshooting
The cause of an electrical problem may be a loose or
corroded connection in the pin or socket connectors. Check
the connectors to ensure that the pins and sockets are
properly seated and engaged. If the pins and sockets show
any signs of corrosion, use a good quality electrical contact
cleaner or fine sandpaper to clean them. When the pins or
sockets show signs of arcing or burning, it will probably be
necessary to replace them.
Refer to (Table 3-2) and (Table 3-3) for listing of tools
necessary for connector maintenance.
Because the pins and sockets are crimped to the wires, it is
not possible to remove them. Using the proper extraction
tool, remove the pin(s) or socket(s) from the plug or
receptacle. Cut the wire as close to the pin or socket as
possible. After cutting the pin or socket off, the wire will most
likely be too short. Using a wire that is too short will allow
pressure to be applied to the pin or socket and wire where
they are crimped when the pin or socket is inserted in the
plug or receptacle. Add a short length of the same size wire
to the short wire by crimp splice or solder. Use heat
shrinkable tubing or other suitable material to insulate the
splice.
Table 3-1: Comparing Electrical System and Hydraulic
System
ELECTRICAL SYSTEM HYDRAULIC SYSTEM
Alternator Pump
Battery Reservoir
Switches Valves
Wires and Cables Tubes and Hoses
Diodes Check Valves
Volts PSI or kPa
Amps gpm or L/min
Ohms Resistance
CAUTION
Burn Hazard!
When possible, ensure the battery is disconnected before
performing any maintenance on an electrical circuit which
is not fused.
If it is necessary to perform electrical maintenance on live
or hot circuits, remove all rings, watches, and other
jewelry before performing maintenance as serious burns
may result from accidental grounding or shorting circuits.
CAUTION
Electrical Fire or Equipment Damage Hazard!
Never replace original wiring with wiring of a smaller size
(gauge). Fire or other damage to the machine may result.
!
!
CAUTION
Electrical Shock Hazard!
Some troubleshooting procedures require testing live
(energized) components. Perform these steps observing
good safety practices to avoid electrical shock injury.
!