Electrical

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Electrical

• Electricity
• Fuses
• Relays
• Solenoids
• Electrical Testing

• Wiring Harnesses
• Testing
• Voltage Drop Testing
• Test Procedures
• Cables/Connections
• Glow Plugs

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What is Electricity?

• The flow of electrons from atom to atom in a
  conductor
• Electricity is based on a theory- an unseen
  force because the energy itself cannot be seen,
  heard, touched, or smelled

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Fuses- devices used to protect the electrical
circuit from too much current flow

• A fuse is designed to open the circuit when the
• current reaches a predetermined level.
• Fuses are rated in Amps
• Do not install a fuse larger than is designed for
  
• the circuit

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Why Use Relays?

• To direct electricity to a high current device
  like a
• starter motor, with the use of a light duty
  switch
• (key switch)
• To control devices

-A relay is a switch that changes states when
voltage is applied to its input. The input
connects to an electric coil. When voltage is
replaced across the input, the coil magnetizes
and moves a switch contact.
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Why Use Relays?

• Relay we use has a single switch that is normally
  open
• (N.O.)- refers to the effect of the switch in
  its normal
• (non-energized state)
• Electric symbol we use for these
• relays - the symbol shows the coil
• and switch

-When the coil is not energized a spring keeps
the switch held open or OFF. When the coil is
energized the magnetic field pulls the switch
against the normally open contact thereby
closing the switch.
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Starter motor solenoid or magnetic switch

• Consists of a contact plate, plunger, plunger
  shaft,
• pull-in coil, hold in coil and return spring
• -When power is applied to coil terminal (key
  turned to start), current
• flows through pull in and hold in coils.
  Magnetic field pulls in plunger
• (the end of plunger has a contact disc). Disc
  makes contact with the
• two main contacts and an R terminal contact.
  Battery is connected to
• one main contact and the starter motor is
  connected to the other.
• Current flows between the battery and starter
  motor. Current also
• bypasses the pull in coil. The hold in coil
  continues to keep the solenoid
• energized until the key switch is opened. At
  that instant current no longer
• flows through the hold in coil and the contact
  disc is spring returned and
• starter motor quits turning.

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Solenoid- a coil of wire

• When voltage is placed across ends of coil, coil
• magnetizes (magnetism moves a plunger)
• Cut away view of coil commonly found on hydraulic
  
• control valves
• Solenoids often take the place of what use to be
  done by mechanical
• linkages, levers and switches.
• -Common uses for solenoids are to control
  mechanical, hydraulic and
• electric circuits.

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Sensors

• Sensors (referred to as senders) - devices that
  respond
• to a physical stimulus
• Variable Resistive Sensors - as physical property
  
• changes, resistance of sensor changes
• Variable Capacitance Sensors - (engine oil
  pressure and
• hydraulic oil charge pressure)
• three wires to these sensors ground lead,
  supply voltage lead
• and sensor signal
• Variable Capacitance sensors- have a circuit
  built into them.
• The circuit converts the capacitance to an
  output voltage proportional
• to the pressure. As the pressure increases
  the voltage increases.

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Sensors

• Switch sensors (air filter and hydraulic filter)
• close or open when the physical property reaches
• predetermined level

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Testing

• Harnesses - Suspected defect in a wire
• test for continuity with an ohm meter
• after checking for continuity, check for a short
  to nearby
• pins, battery ground and battery positive
• Switches - Test leads on correct pins
• With wires disconnected from the switch, connect
  ohm
• meter across the switch
• Switch can often be tested with a voltmeter in a
  live circuit
• -With the switch open you should read infinite
  ohms. With the switch
• closed you should read zero ohms.
  Anything other than these
• readings indicates a faulty switch.

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Testing

• Relays - Test activation signal
• May be able to test for activation signal by
  listening to
• the relay
• Test switch output
• same test for any other switch
• activate the relay and check that the switch
  functions
• properly
• -Activation Signal- When activated and or
  deactivated, many relays make a
• clicking sound. If the clicking sound is
  present, you can generally assume that
• the activation signal is present. A more
  positive method is to check for ground
• and the correct activation signal at the relay
  using a volt meter. If you do not
• have the activation signal, the relay coil was
  shorted and should be replaced.
• If you do not have the activation signal, the
  cause for this must be found.

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Testing

• Relays Quick Testing Tips
• Replace relay with a known good relay
• quick and effective
• Remove relay and put a jumper across correct pins
  to
• simulate a closed switch
• if output circuit functions, the circuit is ok

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Testing

• Modules / Controllers
• First, check for correct ground and power to
  module
• If a known good module is available, replacement
  is
• the best test
• Observe symptoms
• Often controllers are expensive
• casual controller replacement is not recommended
• -Because modules often are complex internally and
  perform many
• functions, it can be difficult to determine if a
  problem exists.

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Voltage Drop Testing

• Voltage drop- the difference in voltage potential
  when
• measured across a circuit or component creating
  resistance
• -Voltage Drop- Resistance decreases the amount
  of voltage available.
• Resistance- an opposing force, created by a
  circuit or
• component, to the flow of electrical current
• -Resistance- There is a small amount of natural
  resistance when voltage
• flow through wires, switches, grounds or
  connections. The resistance
• increases beyond acceptable limits if corrosion
  develops, fittings become
• loose or wires fray. Resistance increases each
  time something, such as a
• wire, a switch, connections, or the ground are
  added to the circuit.

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What Else Should be Tested

• Each wire, ground, connector, switch, solenoid
  and the
• complete circuit should be tested
• Each connection point is a potential source of
  increased
• resistance