JLG 3394RT Service Maintenance Manual page 187

Service - Voltage Reading
DO NOT PIERCE WIRE INSULATION TO TAKE VOLTAGE READINGS.
It has been common practice in electrical troubleshooting to probe wires by piercing the insulation with a sharp point. This
practice should be discouraged when dealing with the AMPSEAL plug assembly, or any other sealed connector system. The
resulting pinholes in the insulation will allow moisture to invade the system by traveling along the wire strands. This nullifies
the effectiveness of the connector seals and could result in system failure.
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SECTION 6 - GENERAL ELECTRICAL INFORMATION & SCHEMATICS
Figure 6-11. Connector Installation
– JLG Sizzor – 6-9