Knowing how a component fails most of the time can help you to diagnose a circuit problem.
How the following components can fail:
CAPACITOR – Difficult to tell a failure – best to test with special tester,
If suspect, the best way to test for a bad one is to replace it, they are cheap.
CIRCUIT BREAKERS – Mechanical – switch contact are ALWAYS normally (at rest) closed.
Test with an ohmmeter – if they show 1Ώ, replace.
Electronic – Polycarbonate Latching- very reliable
Test for open with ohmmeter.
COILS – Fuel Injector
Relay
Solenoid
Ignition Primary
Ignition Secondary
Any of the above coils can: short to copper and lower their resistance.
become work hardened in time and increase in resistance.
open or short to ground
DC MOTORS – can: open
develop brushes that arc causing radio frequency interference noise.
develop bearings that can seize
develop internal shorts to copper lowering resistance, which increases amp draw
drag – slow down in speed, and increase current draw above fuse or circuit breaker
value.
DIODE – 99 out of 100 diodes will SHORT when they fail rather than open.
FUSES – open
never do a visual on a round glass cartridge fuse, they can open on the end under
the metal cap and you will never see it. Always use a test light or meter on glass
fuses to test if they are open.
IC – INTEGRATED CIRCUIT – made up of diodes, resistors, and transistors.
RESISTOR – Always OPEN – will always increase in value before they open.
A resistor will never short circuit or partially short circuit.
SWITCH CONTACT – resistance increase, sometimes weld together.
can stay OPEN.
TRANSISTOR – Usually SHORT, but can open.
The one thing that can accelerate the failure of all of the above components is heat! ©

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