C 3500 Truck 2WD V8-454 7.4L VIN J SFI (1999)
circuit the fusible element will melt and create an open or incomplete circuit. Fuses are an one time protection device and must be replaced each time the
circuit is overloaded. To determine if a fuse is open, remove the suspected fuse and examine the element in the fuse for an open (break). If not broken,
also check for continuity using a J 39200 DMM or a continuity tester. If the element is open or continuity is suspect, replace the fuse with one of equal
current rating.
Circuit Breakers
A circuit breaker is a protective device that is designed to open the circuit when a current load is in excess of the rated breaker capacity. If there is a short
or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. Two types of circuit
breakers are used.
Circuit Breaker: This type opens when excessive current passes through it for a period of time. It closes again after a few seconds, and if the cause of
the high current is still present, it will open again. The circuit breaker will continue to cycle open and closed until the condition causing the high current
is removed.
Positive Temperature Coefficient (PTC) Circuit Breaker: This type greatly increases its resistance when excessive current passes through it. The
excessive current heats the PTC device, as the device heats its resistance increases. Eventually the resistance gets so high that the circuit is effectively
open. Unlike the ordinary circuit breaker the PTC unit will not reset until the circuit is opened, by removing the voltage from its terminals. Once the
voltage is removed the circuit breaker will re-close within a second or two.
Fusible Links
Fusible link is wire designed to melt and break continuity when excessive current is applied. It is often located between or near the battery and starter or
electrical center. Use a continuity tester or a J 39200 DMM at each end of the wire containing the fusible link in order to determine if it is broken. If
broken, it must be replaced with fusible link of the same gage size.
Repairing a Fusible Link
IMPORTANT: Fusible links cut longer than 225 mm (approx. 9 inches) will not provide sufficient overload protection.
Refer to Splicing Copper Wire Using Splice Clips. See: Wiring Repairs/Typical Electrical Repairs/Splicing Copper Wire Using Splice Clips
Repairing Damaged Wire Insulation
Wire Size Conversion Table
If the conductive portion of the wire is not damaged, locate the problem and apply tape around the wire. If the damage is more extensive, replace the
faulty segment of the wire. Refer to Splicing Copper Wire Using Splice Clips See: Wiring Repairs/Typical Electrical Repairs/Splicing Copper Wire
Using Splice Clips and follow the instruction to repair the wire.
Splicing Copper Wire Using Splice Clips
TOOLS REQUIRED
J 38125-B Terminal Repair kit
1. Open the harness.
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If the harness is taped, remove the tape.
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To avoid wiring insulation damage, use a sewing ripper in order to cut open the harness.
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If the harness has a black plastic conduit, pull out the desired wire.
2. Cut the wire.
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Cut as little wire off the harness as possible.
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Ensure that each splice is at least 40 mm (1.5 in) away from other splices, harness branches and connectors. This helps prevent moisture from
