Basic Electrical Systems Theory and Repair

1
Basic Electrical Systems Theory and Repair

• Chapter 29
• Page 387

2
So, Where is Electronics in a Car

• Everywhere
• Antilock brakes, engines, emissions, dash, fuels
  system, transmissions, tires, suspension,
  windows, safety systems, lighting.
• ----Well, I could go on and on and on.

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The Basics
4
Atoms
Positive
Negative
5
Conductors and Insulators
6
Conductors
Conductors A good conductor must not have more
than four electrons in the outer valence ring of
an atom. Copper is one of the best conductors
along with aluminum and gold, conductors have one
electron in the outer valence ring.
7
Insulators
Insulators A good insulator must have more than
four electrons in the outer valence ring of an
atom. Rubber, glass, and porcelain are the best
insulators with many electrons in the outer
valence ring.
8
Electrical Flow
9
Electron Movement
This is the way it really is! Negative to Positive
This is what we are taught! Positive to Negative
10
Wiring is coated with PVC, a flexible plastic to
insulate the copper wiring.
Color Chart
11
Circuit Requirements A full circle is provided
Switch

Source (Battery)
_
Source Battery or voltage supply Load
Electrical components, lights, radio,
etc. Complete path for electron flow Wires and
connections
12
Circuit Devices
Protection Devices

• Controls Devices

Switches for on and off
Fuses and Circuit Breakers Protect form Overloads
13
Fuses and Circuit Breakers
14
Other Symbols
15
Electrical Terms

• Voltage- Also called Electromotive Force,
  Pressure of electricity or the amount of force it
  takes to move electrons. Measured in volts.
• Current- The movement or flow of electrons,
  measured in amperes or amps for short.
• Resistance-Anything that impedes or slows the
  flow of electrons. Measured in ohms.

16
More Electrical Terms

• AC Alternating Current (shop lights and
  equipment)
• DC Direct Current (Auto battery and most
  systems)
• Auto voltage used is normally between 12 and 15
  volts

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Circuit Types
Series Parallel Combination
18
Series Circuit
19
Series Circuits

• Series circuits provide only one path for
  electron flow through a circuit.
• When one component fails, the remaining
  components quit working.

Light
Light
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Parallel Circuit
21
Parallel Circuits

• Parallel circuits provide two or more paths for
  electron flow through a circuit.
• When one component fails, the remaining
  components are not affected.

Lights
12 v
22
Combination

• The simplest type is to use a switch in the first
  part of the circuit (series) and the rest of the
  circuit is wired in parallel.

Lights
12 v
23
Ohms Law
Greg Simon Ohm (1787 1854) Ohms Law It
takes one volt to push one ampere of current
through one ohm of resistance. Look at page 394
for more.
24
Ohms Law
E Voltage (Electromotive Force) I Current
(Intensity) R Resistance (Ohms) E IR I
E/R R E\I
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Ohms Law
E IR I E / R R E \ I
E IR 12 3 X 4
I E / R 3 12 / 4
R E / I 4 12 / 3
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Magnetism
Laws of magnetism 1. Like poles repel each
other. 2. Unlike poles attract each other. 3.
The attractive force increases as the
distance between the magnets decreases.
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Magnetic Fields
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Magnetism
Magnetic Field- Occurs when a current is flowing
through a conductor. Electromagnets- Artificiall
y creating a magnetic field. A coil of wire with
a voltage applied.
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Electromagnets
Switch
Battery
Starter
Solenoid or Relay
30
Electromagnets
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Resistors
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A Few More Terms

• Semiconductors- Can act as both insulator and
  conductor.
• Diode- an electronic one way check valve, it
  allows flow one way but doesnt allow it to
  reverse the other way.
• Transistor- electronic relay. Its very fast, and
  no moving parts.

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Basic Tests

• Meters
• Analog and Digital

Digital Volt-ohm Meter (DVOM) or Digital
Multimeter (DMM)
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Measurements
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Voltage Testing
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Voltage Check
37
Testing Voltage After Switch
Open wire broke or fried wire
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Circuit Test
3
1 12 v 2 12v 3 12v
1
2
2
39
Continuity Testing
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Ohmmeter Test
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Diode Check
Diode is a one way street only. Reversing the
multimeter leads will tell us if the voltage is
allows one way and is stopped the opposite way.
If it doesnt do this toss the diode.
.000 one way and 1. the other.
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Testing Device with Ohmmeter with Power Removed
Continuity Should be .000 if Good
Infinity Should be 1. if Bad
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Testing Amps
Need to change red probe lead to Amp on meter
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Test Light
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Test Light
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Using a Jumper Wire
Bypassing Ground
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Bypass a Switch with Jumper Wires
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Circuit Defects
Open Incomplete or broken circuit. The circuits
quits working. Short Two wires unintentionally
connecting with each other. Could cause more
than one component to operate.
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Circuit Defects
Ground When a positive and negative wire contact
each other. Could cause sparking and extreme
heat due to high current flow. Very low
resistance blows fuses, circuit breakers, or
fusible links.
50
Circuit Defects
Open Circuits
51
Circuit Defects
Short Circuits
52
Circuit Defects
Ground Circuits
53
Your Job.

• Complete chapter Questions 1-15 (review) and 1-10
  (ASE-style). Page 401-402
• Write on a separate paper and write out the
  complete question and your answer. ( do not write
  the other answer options).
• Complete the chapter worksheet (I will give it
  out). You may write on it.
• File all items in your note book.
• Notebooks will be graded in the future.