OPERATOR’S STATION
ELECTRICAL SYSTEM
TM 5-3805-258-24-1
SYSTEMS OPERATION
2.
3.
TROUBLESHOOTING METHODS
Most of the connections between harnesses are
made with rubber plugs. If these connections are
not tight they can cause several different prob-
lems at one time (several different circuits go
through one plug). They can also cause intermit-
tent (come and go) problems. Make sure the
rubber plugs are tight before other tests are
done.
Use the 5P7277 Voltage Tester to test a circuit
for voltage instead of a VOM (volt-ohm-mil-
liammeter). A VOM may show voltage when
there is a bad connection which will not carry
enough current.
Use the 8S4627 Circuit Tester to test circuits
without voltage for continuity. The light in the
5 P 7 2 7 7 V O L T A G E T E S T ER
4.
8S4627 Circuit Tester is dim (not much light)
with a 10 ohm resistance in the circuit. It be-
comes brighter (more light) with less resistance.
The 8S4627 Circuit Tester can also be used to
test diodes. The pointer of the tester is positive
(+) if the batteries are installed correctly. The
tester light must be dim with the point of the
tester connected to the base (anode) of the diode
It should not be on at all when
it is connected in the reverse direction with the
point connected to the cathode of the diode
Failure of an electrical component can cause or
be caused by the failure of one or more other
components. Always find the cause of a failure
of an electrical component before making a re-
placement of the component.
8 S 4 6 2 7 C I R C U I T T E S T ER
BLOCK DIAGRAM
The block diagram of the 950B electrical system shows the flow of electricity
to the different parts of the system. It does not show all components, wires and
connections. The block diagram shows which components work together.
The fuses shown in the block diagram are on a fuse panel under the instru-
ment panel.
The dashed (broken) lines in the block diagram are an indication of a control
connection, for example a switch that controls a relay.
There is a solid state operator panel in the instrument panel. The indicators
on the operator panel are light emitting (give off light) diodes (LED’s) and are
part of the operator panel. They are not replaceable. There are many tempera-
ture and pressure switches connected to the operator panel. The operator panel
makes a measurement as to whether the switches are open or closed and from
this information, turns on an indicator when necessary. It also can turn on the
master fault light and the fault alarm. The block diagram shows the switches
that are connected to the operator panel. Make reference to the individual
circuit descriptions for more information about an individual circuit.
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