JLG 530LRT, Service And Maintenance Manual

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SECTION 7 - GENERAL ELECTRICAL INFORMATION & SCHEMATICS
3121781 7-15
7.6 SWITCHES
Basic check
The following check determines if the switch is func-
tioning properly, not the circuit in which the switch is
placed. A switch is functioning properly when there is
continuity between the correct terminals or contacts
only when selected.
1. De-energize the circuit.
2. Isolate the switch from the rest of the circuit if possi-
ble. If not possible, keep in mind it may affect read-
ings.
3. Access the terminals to the switch.
4. If the switch has two terminals:
a. Measure resistance across the terminals.
b. Change the switch position.
c. Measure resistance again with the leads in the
same positions. If the meter was reading short,
it should read an open. If the meter was read-
ing open it should read short.
5. If the switch has more than two terminals, consult
the schematic or switch diagram to determine what
terminals will be connected. The test is similar to
testing a switch with two terminals.
a. Place one meter lead on the common contact
and the other on a different contact in the
same circuit.
b. Cycle through all positions of the switch. The
meter should read short only when the switch
connects the two terminals and open other-
wise.
c. If the switch has more than one common con-
tact repeat the process for that circuit.
Leveling Jacks Limit Switch
Limit switches are used to control movement or indicate
position. Mechanical limit switches are just like manu-
ally operated switches except that the moving object
operates the switch. These switches can be tested the
same way as a standard switch by manually operating
the sensing arm.
Another type of limit switch used by JLG is the inductive
proximity switch, also referred to as a “prox switch”.
Inductive proximity switches are actuated only by fer-
rous metal (metal that contains Iron, such as steel) near
the switch. They do not require contact, and must be
energized to actuate. These types of switches can be
used to detect boom or platform position, for example.
These switches have a sensing face where the switch
can detect ferrous metal close to it. To find the sensing
face, take note how the switch is mounted and how the
mechanisms meet the switch. Test this type of switch as
follows:
1. Remove prox switch from its mount.
2. Reconnect harness if it was disconnected for step a,
and turn on machine.
3. Hold switch away from metal and observe switch
state in the control system diagnostics using the
Analyzer. See vehicle or control system documenta-
tion on how to do this.
4. Place sensing face of switch on the object to be
sensed by the switch. If that is not available, use a
piece of ferrous metal physically similar to it. The
switch state in the control system diagnostics should
change.
5. When reinstalling or replacing switch be sure to fol-
low mounting instructions and properly set the gap
between the switch and object sensed.