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GI-50 < BASIC INSPECTION > SERVICE INFORMATION FOR ELECTRICAL INCIDENT • When inspecting a ground connection follow these rules: - Remove the ground bolt or screw. - Inspect all mating surfaces for tarnish, dirt, rust, etc. - Clean as required to assure good contact. - Reinstall bolt or screw securely. - Inspect for “add-on” accessories which may be interfering with the ground circuit. - If several wires are crimped into one ground eyelet terminal, check for proper crimps. Make sure all of the wires are clean, securely fastened and providing a good ground path. If multiple wires are cased in one eye- let make sure no ground wires have excess wire insulation. • For detailed ground distribution information, refer to “Ground Distribution” in PG section. VOLTAGE DROP TESTS • Voltage drop tests are often used to find components or circuits which have excessive resistance. A voltage drop in a circuit is caused by a resistance when the circuit is in operation. • Check the wire in the illustration. When measuring resistance with DMM, contact by a single strand of wire will give reading of 0 ohms. This would indicate a good circuit. When the circuit operates, this single strand of wire is not able to carry the current. The single strand will have a high resistance to the current. This will be picked up as a slight voltage drop. • Unwanted resistance can be caused by many situations as follows: - Undersized wiring (single strand example) - Corrosion on switch contacts - Loose wire connections or splices. • If repairs are needed always use wire that is of the same or larger gauge. Measuring Voltage Drop — Accumulated Method • Connect the DMM across the connector or part of the circuit you want to check. The positive lead of the DMM should be closer to power and the negative lead closer to ground. • Operate the circuit. • The DMM will indicate how many volts are being used to “push” current through that part of the circuit. SGI853 |