Mechanic How To: Diagnose a Short Circuit


When a circuit is short it can cause a fuse to blow and create an open circuit

When it comes to electrical diagnosis, accessing and understanding common open circuits is a necessary step to fixing problems yourself. With a little help from a high-quality DVOM, some basic understanding of diagrams and some diligence, one can effectively determine differences between open and short circuits to maintain and restore fuses and other systematic areas prone to short-circuiting.

Short circuits are annoying to diagnose, and they occur when an electrical current flows into the ground rather than throughout a load. Due to the path’s ground direction, it maintains significantly less resistance than a load. While electricity doesn’t always take such a route, it will with an increased current. When it does, a blown fuse is a typical result. Blown circuits often melt links, blow fuses and trip circuit breakers.

Diagnosing such a situation requires placing a circuit protection device with “short finders” capable of handling excessive currents flowing within a circuit. If you’re not in possession of one, wire a sealed-beam headlight electric bulb with two leads, and attach several male and spade terminals. When accessing materials for such an adventure, be sure to check out online resources like SWengines for additional information.

Understanding power distribution outlines may be difficult, and descriptions tend to differ with each diagram. It’s important to locate solid black dots, as they dictate a fuse upon a system’s circuit. Once the fuse is located, and once it’s been determined as a problem source, make a list. Then, disconnect one system at a time to slowly remedy the problem. Several wiring diagrams provide several system circuit lists pertaining to fuses, and some provide a diagram of actual wiring. If the latter is provided, be careful when making choices, and don’t accidentally miss a circuit connected to a fuse.

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