Download MLR: Electrical Study Guide

MLR: Electrical Study Guide
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Chapter 6: Diagnosing Using Wiring Diagrams
With an understanding of Voltage, Current, and Resistance, we can now turn our attention back to the
devices that determine those values.
Circuit Protectors
As introduced in Module 2, three types of circuit protectors
Circuit Protectors
are used in modern automotive applications: fuses, circuit
breakers, and fusible links. The primary function of these
Circuit protectors are used to prevent
devices is to protect the wiring from damage should a circuit
wiring damage from excessive current.
failure cause excessive current. Although circuit protectors
are rated in amps, it is actually the heat caused by too much current that causes the device to open the
circuit.
Fuses
Fuses are the most common circuit protectors in automotive use and are rated from 5 A to 80 A. They
are one-use devices with a metal strip inside that melts from the heat caused by exceeding the current
rating of the strip. The most common fuse types are the ATC/ATO (Auto Fuse or blade style), Mini Fuse,
and Maxi Fuse. As shown in the graph here, different colors are used to identify the amperage values of
the various fuses.
Assorted Automotive Fuses
Fuse Colors
Circuit Breakers
Unlike fuses, circuit breakers can be reset, either manually or
automatically, and reused. Circuit breakers are either "cycling" or
"non-cycling.”
Circuit Breakers
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Circuit breakers can be either
cycling or non-cycling