Download MLR: Electrical Study Guide

MLR: Electrical Study Guide
©2013 Melior, Inc.
4. If one headlamp does not obtain full brightness or burn dim the HID headlamp is nearing the end of
its useful life.
It is recommended by manufacture that HID headlight be replaced in pairs. Over time HID headlight will
not illuminate as they once did when they were new.
Using an electrical wiring diagram
A wiring diagram is an extremely valuable tool when diagnosing an electrical concern in any type of
equipment or vehicle. The proper use of a wiring diagram will reduce diagnostic time. There are several
different methods advanced by different automotive manufactures and textbook authors. Some
recommend always starting at the power source when testing an electrical circuit. Other manufactures
teach starting at the malfunctioning component and backwards testing the circuit. Still other
recommends starting at the fuse box or relay, (if the circuit is relay controlled). Before beginning
diagnostic on an electrical circuit it is recommended that a technician review circuit operation. Some
manufacture used slightly different schematic symbols to identify components.
Note: Always follow manufacture diagnostic procedure when diagnosing electrical systems. Failure to do
so could result in personal injury or death, damage to electrical system, or improper diagnostic.
Using a Test Light to Test Electrical Circuits
CAUTION: Never use a test light to test low voltage circuit. Doing so may damage or destroy expensive
electronic components. On vehicles equipped with electronic control modules only use a test light when
directed by a manufacture diagnostics test procedure.
A test light is a useful and reliable tool when used correctly. A test list can be used to test for open
circuit, closed circuits, and short circuits. In a closed circuit, the test light will illuminate when connected
to a circuit that has a current flowing on the power side. On an open circuit, a test light will not
illuminate if there is no current flowing when connected after the opening in the circuit. A test light can
be used to test for a short circuit if connected in series with the short circuit.
Normal Circuit
Open Circuit
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