Free ASE PREP from my BAR Specific Diagnostic Course: Relays
Reading Wiring Schematics:
When reading a wiring diagram there are a few things you have to keep in mind:
Locate the power source, it’s usually on top and flows down towards the ground circuit, but there are exceptions to that rule.
Locate the component in question
Locate the ground for the circuit you are troubleshooting
Understand how to read the wire colors and location of connectors and splices.
Have a good understanding of the symbols, use the information data sheet before hand
I.D. the circuit numbers and terminal ID
Now we are going to walk through a few wiring schematics to help you have a better understanding of the electrical road map.
There are at least two circuits in a relay, a low current circuit and a higher current circuit.
The lower current circuit controls the higher current circuit which could be a fan, horn or even power windows.
There are several components on a vehicle that uses relays, basically this is a device that uses low current to control a higher amperage circuit as I said earlier.
This control unit contains an iron core, a mobile contact set of points and a coil to build magnetism. Theses switches are usually build (N/C) normally close or (N/O) normally open. Once they are energize the opposite reaction will happen.
For an example if it’s normally close, once energize it will open, and if it’s normally open once energize it will close.
Once current flows through the coil a magnetic field is builded and then the contact points will close, current will then flow through the contacts out one of the pin contacts to a certain component, for example a fan motor.
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