Mechanic Glossary

Circuit Breaker

A resettable electrical safety device that automatically cuts off power to a circuit when current exceeds a safe limit.

Unlike standard fuses that melt and must be replaced, a circuit breaker is resettable. It protects electrical circuits from overloading. It uses a internal bimetallic strip or electromagnet. When current is too high, the heat bends the strip, releasing a latch that breaks the contact. Once the strip cools down, you press a button or switch to reset it. They are used for high-draw accessories like power seats, window motors, and trailer tow packages.

Breakers are safer because they do not leave you stranded without a spare. However, if a breaker trips repeatedly, do not just keep resetting it. You have a short-to-ground or a bound electric motor drawing too much current that must be diagnosed to prevent wiring fires.

Frequently Asked Questions

A fuse is a one-time safety device containing a metal strip that melts when overloaded, requiring replacement. A circuit breaker is a mechanical switch that trips when overloaded and can be reset and reused multiple times.
It is a breaker that resets itself automatically after cooling down. Commonly used on headlights and windshield wipers, it ensures you don't lose vision or lights permanently on dark highways due to a temporary overload.
The window glass tracks are sticky, or the motor gear is binding. The motor has to work harder to raise the glass, drawing high current that trips the breaker.
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