SECTION 6 - GENERAL ELECTRICAL INFORMATION & SCHEMATICS
3121642 – JLG Lift – 6-1
SECTION 6. GENERAL ELECTRICAL INFORMATION & SCHEMATICS
6.1 GENERAL
This section contains schematics to be used for locating and correcting most of the operating problems which may develop. If a prob-
lem should develop which is not presented in this section or which is not corrected by listed corrective actions, technically qualified
guidance should be obtained before proceeding with any maintenance.
IT IS A GOOD PRACTICE TO AVOID PRESSURE-WASHING ELECTRICAL/ELECTRONIC COMPONENTS. SHOULD PRESSURE-WASHING BE UTILIZED TO WASH AREAS CON-
TAINING ELECTRICAL/ELECTRONIC COMPONENTS, JLG INDUSTRIES, INC. RECOMMENDS A MAXIMUM PRESSURE OF 750 PSI (52 BAR) AT A MINIMUM DISTANCE OF
12 INCHES (30.5 CM) AWAY FROM THESE COMPONENTS. IF ELECTRICAL/ELECTRONIC COMPONENTS ARE SPRAYED, SPRAYING MUST NOT BE DIRECT AND BE FOR
BRIEF TIME PERIODS TO AVOID HEAVY SATURATION.
6.2 MULTIMETER BASICS
A wide variety of multimeters or Volt Ohm Meters (VOM) can
be used for troubleshooting your equipment. A digital meter
with reasonable accuracy (within 7%) is recommended for the
measurements in these procedures. This section shows dia-
grams of a common, digital VOM configured for several differ-
ent circuit measurements. Instructions for your VOM may vary.
Please consult the meter operator’s manual for more informa-
tion.
Grounding
"Grounding the meter" means to take the black lead (which is
connected to the COM (common) or negative port) and touch
it to a good path to the negative side of the voltage source.
Backprobing
To "backprobe" means to take the measurement by accessing
a connector’s contact on the same side as the wires, the back
of the connector. Readings can be done while maintaining cir-
cuit continuity this way. If the connector is the sealed type,
great care must be taken to avoid damaging the seal around
the wire. It is best to use probes or probe tips specifically
designed for this technique, especially on sealed connectors.
Whenever possible insert probes into the side of the connec-
tor such that the test also checks both terminals of the con-
nection. It is possible to inspect a connection within a closed
connector by backprobing both sides of a connector terminal
and measuring resistance. Do this after giving each wire a gen-
tle pull to ensure the wires are still attached to the contact and
contacts are seated in the connector.
Min/Max
Use of the "Min/Max" recording feature of some meters can
help when taking measurements of intermittent conditions
while alone. For example, you can read the voltage applied to
a solenoid when it is only operational while a switch, far from
the solenoid and meter, is held down.
Polarity
Finding a negative voltage or current reading when expecting
a positive reading frequently means the leads are reversed.
Check what reading is expected, the location of the signal and
that the leads are connected to the device under test correctly.
Also check that the lead on the "COM" port goes to the ground
or negative side of the signal and the lead on the other port
goes to the positive side of the signal.
Scale
M = Mega = 1,000,000 * (Displayed Number)
k = kilo = 1,000 * (Displayed Number)
m = milli = (Displayed Number) / 1,000
μ = micro = (Displayed Number) / 1,000,000
Example: 1.2 kΩ = 1200 Ω
Example: 50 mA = 0.05 A
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