Jacobsen AR3, Техническое руководство по ремонту

Страница: 104 / 342

ELECTRICAL
4181384 First Edition 4-47
4
Instrumentation Circuit—Theory of
Operation
Power Circuit
Unswitched power is available to key switch terminal 30
and to multi-function gauge terminal (8) through 2-amp
fuse F5.
When the key switch is turned to the run position, current
flows from the AC terminal of the key switch through
10-amp fuse F10 to control module terminals 3 and 8,
powering up the module. Current also flows to
multi-function gauge terminal 2 from 5-amp fuse F8,
powering up the gauge.
Engine Oil Pressure Light
When the key switch is in the run position, voltage is
available to engine oil pressure light from 5-amp fuse F9.
When the engine oil pressure is below 7 psi (0.483 bar),
the engine oil pressure switch contacts close. With the
switch contacts closed, a ground is provided to the
engine oil pressure light, turning on the light.
Hydraulic Filter Light
When the key switch is in the run position, voltage is
available to hydraulic filter light from 5-amp fuse F9.
The hydraulic filter switch is a differential pressure switch.
The switch closes when there is a 50 psi (3.447 bar) drop
between the inlet and outlet pressures of the filter. When
the switch closes, ground is provided through the switch
to the hydraulic filter light, turning on the light.
Engine Over-Temperature Circuit
The engine coolant temperature switch closes when the
coolant temperature reaches 230°F (110°C). When the
switch closes, a ground is provided through the switch to
the control module over-temp input terminal, activating
the input. With the input activated, current flows from 12V
over-temp light output to the over-temp light, turning on
the light.
Current also flows from 12V over-temp light output to the
alarm, activating the alarm.
Multi-Function Gauge
Fuel Level Sender Input
The float attached to the fuel level sender moves as the
fuel level changes to various levels. The resistance of the
fuel level sender changes in relationship to the position of
the float. The resistance of the sender will vary between
4 and 180 ohms. When the fuel tank is full the sender
resistance is 4 ohms and when the fuel tank is empty the
sender resistance is 180 ohms. The multi-function gauge
fuel level input terminal measures the resistance
between the fuel level sender and ground. The
multi-function gauge calculates the fuel level from the
resistance reading and the result is displayed on the LCD
display.
Setup Switch Input
When the setup switch is held in the depressed position,
voltage is provided to the multi-gauge setup enable input
terminal, activating the input. With the input activated,
various gauge functions can be accessed. For more
information, see “Safety, Operators & Maintenance
Manual”.
Hour Meter Enable Input
The hour meter enable input provides control of when to
allow the hour meter to start logging hours. The hour
meter enable circuit is controlled by the alternator light
circuit. (See “Charging Circuit—Theory of Operation” on
page 4-24.)
Battery Discharge input
The battery discharge input monitors the battery voltage.
When the battery voltage falls below a preset level, the
battery icon blinks on the multi-function gauge.