OPERATOR’S STATIONELECTRICAL SYSTEMTM 5-3805-258-24-1SYSTEMS OPERATION2.3.TROUBLESHOOTING METHODSMost of the connections between harnesses aremade with rubber plugs. If these connections arenot tight they can cause several different prob-lems at one time (several different circuits gothrough one plug). They can also cause intermit-tent (come and go) problems. Make sure therubber plugs are tight before other tests aredone.Use the 5P7277 Voltage Tester to test a circuitfor voltage instead of a VOM (volt-ohm-mil-liammeter). A VOM may show voltage whenthere is a bad connection which will not carryenough current.Use the 8S4627 Circuit Tester to test circuitswithout voltage for continuity. The light in the5 P 7 2 7 7 V O L T A G E T E S T ER4.8S4627 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 totest diodes. The pointer of the tester is positive(+) if the batteries are installed correctly. Thetester light must be dim with the point of thetester connected to the base (anode) of the diodeIt should not be on at all whenit is connected in the reverse direction with thepoint connected to the cathode of the diodeFailure of an electrical component can cause orbe caused by the failure of one or more othercomponents. Always find the cause of a failureof 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 ERBLOCK DIAGRAMThe block diagram of the 950B electrical system shows the flow of electricityto the different parts of the system. It does not show all components, wires andconnections. 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 controlconnection, for example a switch that controls a relay.There is a solid state operator panel in the instrument panel. The indicatorson the operator panel are light emitting (give off light) diodes (LED’s) and arepart of the operator panel. They are not replaceable. There are many tempera-ture and pressure switches connected to the operator panel. The operator panelmakes a measurement as to whether the switches are open or closed and fromthis information, turns on an indicator when necessary. It also can turn on themaster fault light and the fault alarm. The block diagram shows the switchesthat are connected to the operator panel. Make reference to the individualcircuit descriptions for more information about an individual circuit.3-141
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