Auto Repair Help
Carl’s Corner – Auto Repair Help

DIAGNOSE – FUSES REGULARLY BLOW
By Carl O’Reilly

SYMPTOM SUMMARY
An electrical fuse continues to blow once replaced.

USUAL CAUSE
A fuse is designed as an electrical protection device. It is designed to blow or open the affected electrical circuit when the current flow in the protected circuit reaches unsafe levels. Once blown, the fuse prevents electrical power from reaching the devices that are on the circuit. This prevents the wires from melting causing severe damage or fire to the electrical system. Occasionally, a fuse will blow without an apparent cause. Once replaced, the system will function normally and will not blow again. If a fuse continues to blow once replaced, it is an indication of an electrical short circuit to ground. This can be caused by a failed electrical component, bare wires touching the vehicles body (ground) or something as simple as a foil gum wrapper in the cigarette lighter socket. An incorrect fuse or to low of an amperage for the protected circuit can also be the cause.

CORRECTIVE ACTION
Electrical diagnosis and short circuit tracing requires the use of a vehicle specific wiring diagram. The diagram will provide a road map of the vehicles electrical system. It will also indicate how the circuits are interconnected and any splices that are in the harness. Troubleshooting a short circuit without the appropriate wiring diagram will be difficult at best.

PRECAUTIONS, TIPS and NOTES
You can obtain a short circuit tracer at most auto parts stores. This device is pulled accross the outside of the electrical harness and reveals high current loads that indicate a short circuit. This can aid in detecting where the electrical short is located. It is available for a nominal charge and includes instructions for proper use.

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