Schematics and troubleshooting

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Schematics and troubleshooting

• Wiring schematics
• Locating short circuits
• Electrical troubleshooting diagnosis

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Wiring schematics

• Complex schematics are usually broken down to
  individual circuits
• Schematics of individual circuits show
• Power side
• Ground side
• Splices
• Connections
• Electrical components
• Some information may be referenced in another
  circuit schematic

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Wiring schematics

• Wire coloring is abbreviated (abbreviation is not
  necessarily standardized)
• First color is the base color
• Second color is the trace or stripe and separated
  by a /
• Wire size is usually noted
• Connectors are denoted by a symbol and numbered

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Wiring schematics
Always verify wire color coding on vehicle Dont
assume schematic color is correct
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Wiring schematics

• Switches are always drawn on diagrams in their
  normal position
• Normally open N.O.
• Normally closed N.C.
• Poles refer to number of circuits completed by
  switch
• Throws refer to number of output circuits

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Wiring schematics
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Schematic symbols
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Wiring schematics
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Wiring schematics
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Locating short circuits

• Short circuit an electrical connection to
  another wire or to ground before the circuit load
  
• Isolate circuit that is shorted from other
  circuits that are powered by a common fuse
• Determine whether short is constant or
  intermittent

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Locating shorts

• Install resetting circuit breaker in circuit or
• Install test light in place of fuse or breaker
• Installing either a circuit breaker or test light
  allows the circuit to be powered while diagnosis
  is completed
• Check wiring schematic for circuit routing

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Locating shorts

• Common areas of potential damage
• Wiring around sources of high heat
• Harnesses that are subject to movement
• Harnesses that are near the battery or exposed
  under chassis, or passenger compartment
• For intermittent shorts, wiggle harnesses and
  connections while watching test light

13
Electrical troubleshooting diagnosis

• Information from customer
• When did problem start occurring?
• Under what conditions?
• Previous repairs
• Verify complaint
• Visual inspection
• Check for other non-operative circuits that may
  be related

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Electrical troubleshooting diagnosis

• Check TSBs for pattern failures
• Study circuit diagram and understand how circuit
  works
• Power source
• Ground path
• Power flow
• Isolate problem to a particular area of the
  circuit
• Determine cause and repair vehicle