Textron JACOBSEN R-311 69166, Technical/Repair Manual

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ELECTRICAL
4203781 First Edition 4-59
4
Horn/Test Circuit—Theory of
Operation
Unswitched Power Circuit
Unswitched power is available from the battery positive
terminal to the starter motor battery terminal and then
from the starter motor battery terminal to 50-amp circuit
breaker (F1) battery terminal. Unswitched power is
available through the 50-amp circuit breaker (F1) to
30-amp circuit breaker (F2) input terminal and from
circuit breaker (F2) input terminal to 10-amp circuit
breaker (F5).
Unswitched power is available from 30-amp circuit
breaker (F2) output terminal to accessory relay terminal
30.
Unswitched power is provided from 10-amp circuit
breaker (F5) to PTO switch terminal E and then from
terminal E to time delay relay +12V terminal.
Interlock Circuit
The interlock circuit provides 12 volts to the key switch.
The following must occur before the key switch is
provided with 12 volts:
• PTO switch in the off position
• Park brake switch in the on position
With the PTO switch in the off position and park brake
switch in the on position, voltage is provided from the
park brake switch to key switch terminal B.
Switched Power Circuit
When the key switch is turned to the run position, voltage
is provided from key switch terminal I to accessory relay
terminal 86, energizing the relay. With the relay
energized, switched power is provided from accessory
relay terminal 87 to 10-amp circuit breaker (F6) and
10-amp circuit breaker (F4).
Switched power is provided from 10-amp circuit breaker
(F6) to horn relay terminals 30 and 86.
Switched power is provided from 10-amp circuit breaker
(F4) to the gauges and the indicator lights.
Horn/Test Circuit
When the horn/test switch is pressed, the horn sounds
and the following indicator lights turn on:
• Air filter service light
• Return filter service light
• Hyd oil temp light
• Charge filter service light
• Engine coolant temp light
When the horn/test switch is in the on position, a ground
is provided through diode (V3) to the air filter service
light, turning on the light. Ground is also provided through
diode (V4) to the return filter service light, turning on the
light. Ground is also provided through diode (V5) to the
hyd oil temp light, turning on the light. Ground is also
provided through diode (V7) to the charge filter service
light, turning on the light. Ground is also provided through
diode (V1) to the engine coolant temp light, turning on the
light.
With the horn/test switch in the on position, two ground
paths are provided to the horn relay. Ground is provided
through diodes (V1 and V2) and diodes (V5 and V6) to
horn relay terminal 85, energizing the relay. With the
relay energized, voltage is provided from horn relay
terminal 87 to the horn, turning on the horn.