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Diagnose Electrical Accessories
It is easy to diagnose electrical accessories
If you can read wiring diagrams
Quiz #20
• Blower Motor works on HIGH only
• What might cause this?
Warning Systems
• Most systems will ground a buzzer or
warning lamp
Gauges
• Explore the operation of a bimetallic dash gauge
Bimetallic Gauges
• As voltage increases what happens to amp
flow?
• Many dash gauges use an
Instrument Voltage Regulator (IVR)
to keep a constant 5 volts to the gauges
Diagnose dash gauges
• Notice if all gauges are out or only one
• Use a test light to ground the sending unit
wire
• Do not use this technique with digital dash
Two Coil Magnetic Gauges
Three Coil Magnetic Gauges
Diagnosing Gauges
• Some gauges can be damaged by grounding
sending unit wire
• Digital Dash gauges may send 5 volt
reference to sender
• Use diagnostic charts to diagnose digital
gauges
Instrument Clusters
• Use caution when handling printed circuit
boards
• Finger prints can cause high resistance and
eventual open circuits in printed circuits