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8/10/2019 ESD 1 Electrical Components
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Circuit Protection
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Circuit Protection
Types of Fused Protection
How to
pull them
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FusesAuto-fuse
(blade type
and Color
coded)
Mini-fuseMaxi-fuse A. TEST HOLES
B. REMOVAL
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Maxi-fusesCombination blade / cartridge
Protects main circuitsSafer than fusible link
Cover fewer circuits than a
fusible link
Often in Power Distribution box
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Ceramic and Glass
Rated by current failure level
Three letter code for type and size
Glass style replaces ceramic
Caution in pulling
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Two reasons for blowing
Where do they blow?
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New Circuits
What size of
fuse should I
install?
Use Watts law.
Watts dividedby volts
?
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FUSIBLE LINKS
Lighter gauge wire
than main
conductor Covered with
special insulation
Protect Main
circuits
Usually under
hood
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Fusible Links Repair Location Circuits protected
Insulation
Visual checks Installing a new
link
4 wire sizessmaller (4
numbers larger)
Soldering
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Fuses
Male Pal fuses Female Pal fuses Bolt on Pal Fuses
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Circuit Breaker
Why circuit breakers
Styles
Deterioration
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TESTING CIRCUIT
PROTECTION DEVICES Must inspect closely
Type of failure determines cause
Best to use DVOM
Do not overload circuit by installing
to large of fuse or tin foil
Connections must be tight
Do not use un-fused jumper wire
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Electrical Components
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Switches
Controls electrical
current (N.O. or N.C.)
Single-pole, singlethrow (SPST)
Momentary Switch
Single-pole, double
throw switch (SPDT)
Ganged Switch
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TESTING RELAYS
Can use several methods to test
Must Check both circuits
Be careful using test light if relay is
operated by computer
Can bench test if needed
Some relays have schematic on them
Must be correct resistance
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SOLENOIDS
Electromagnetic
device with a iron
core
Does mechanical
work
Core is moveable
and does work Can test with
DVOM
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Usually used to
control fan motor
speeds Resistance is
changed by control
of switch
Controls current to
change speeds
Thermal fuse
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Variable Resisters
Rheostats
Two terminals
Higher current
Potentiometer
Three terminals
Lower current
Many uses for
variable types
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The three types of circuit
defects are:
ShortsGrounds
Opens poor connections
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TESTING FOR CIRCUIT
DEFECTS DVOM IS BEST TO USE!
Must know circuit operation before
can diagnose problem
Must know how to use equipment
and which equipment to use.
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Now, did he say,
Amps, Volts or
Ohms?