Service and Repair Manual April 2017Boom Components18 GTH-1056 Part No. 12781451-1Boom Proximity SwitchThe boom angle switch is a proximity switch. Thisswitch functions by sensing a change in theelectromagnetic field of the switch, due to theintroduction of metal into the field. A proximityswitch is, simply, a metal detector.The switch generates an electromagnetic field atthe face of the switch. This field senses when steelhas been moved close to the switch as well aswhen the steel has been moved away, which is howthe switch contacts open and close.These switches are of a fail-safe design. Should theswitch or the switch wire circuit be faulty, themachine will not function outside its designed rangeof use.The boom proximity switch is a component of thedrive circuit and the chassis sway circuit. Both thedrive and the chassis sway functions are disabledwhen the boom is raised to 60° or higher.How to T est a Pr oxi mity Switc hHow to Test a Proximity Switch1 Remove the switch from the machine. Do notdisconnect the switch wire harness from themachine.2 Start the engine.3 Move the switch away from any ferrous ormetallic objectResult: The light of the limit switch assembly isnot illuminated.4 Move the switch close to any ferrous ormetallic objectResult: The light of the proximity switchassembly turns on. The switch is functioningcorrectly.
