ELECTRICAL TROUBLESHOOTING

TM 5-2420-224-20-1

ELECTRICAL TROUBLESHOOTING

WARNING

Do not remove, install, connect, or disconnect any electrical component unless

vehicle MASTER disconnect switch is OFF. To do so could result in injury to

personnel.

CAUTION

If checking for continuity, MASTER disconnect switch must be OFF to prevent

damage to equipment.

NOTE

If checking for +24 VDC, MASTER disconnect switch must be ON.

Before starting detail troubleshooting procedures, review the wiring diagram to thoroughly

familiarize yourself with the circuit(s) involved. Refer to SEE wiring diagram, NSN 7610-01-475-7996.

Analyze the symptoms and conditions and use common sense and logic to determine the most likely

cause of the problem, then troubleshoot that circuit first. The more information you have concerning

the problem, the easier it will be to troubleshoot.

Isolate to the subsystem level (in cases where more than one subsystem is involved); next

isolate the problem to a single circuit within the subsystem; then, isolate the problem to the faulty

component using the troubleshooting symptom index.

Frayed, broken, loose, or corroded wiring is a common source of problems in any electrical

circuit. Always make visual inspection before starting detail troubleshooting. Observe, in particular,

contacts to ground. Components with case grounds are especially troublesome.

Most of the checks are made by voltage checks. Instructions prior to the step may instruct you

to disconnect at test point from the potential malfunctioning component. Once the check has been

made, either repair the component or go to the referenced step. When ready to make the

prescribed check, apply power to the circuit (if required). A helper may be required if the switch or

power source is out of reach.

When making continuity checks, make sure the test equipment is isolated from the power

source.

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