New Holland CX720 Repair Manual page 190

The current that flows through the switch is not the same as all the current requested by the equipment to be
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operated, but usually by a smaller current: this allows the usage of smaller and less expensive switches;
The distance from the supply, to the equipment, can be made as short as possible to minimise voltage drop.
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There are five styles of relays used on the CX combine. The micro relay (1) is the most commonly used relay, and is
used on all but two locations on the fuse panel in the cab. One mini relay (2) is used in the top left position of the fuse
panel in the cab, while a time delay relay (3) is used in the top right position of the fuse panel for controlling the cab
interior light and side lights. The fourth style of relay is the start relay (4) which is located in the engine compartment.
The fifth style of relay is the grid heater relay (not shown) located on the engine.
On the relay cover there are 4 or 5 terminal markings:
3 or 30: input terminal direct from battery positive, normally live.
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2 or 85: winding output terminal, usually to ground.
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1 or 86: winding input terminal.
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4 or 87: output terminal for normally closed contact.
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5 or 87a: output terminal for normally open contact.
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SOLENOIDS
Solenoids work in much the same way as relays, except that the iron core is not fixed in place. As a result, the
windings in the control circuit cause the iron core to move.
In the starting system, for example, the movement of this core is used to send large amounts of current to the starter
motor.
A solenoid is basically a winding around an iron core. In the centre of the core there is a plunger which is free to
move through the core. When an electrical current passes through the winding an electro-magnetic force is produced
which causes the plunger to move through the core. If the current is switched off, the magnetic force is stopped and
the plunger is returned by a spring.
DISTRIBUTION SYSTEMS - ELECTRICAL POWER SYSTEM
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