I. What Is an Automotive Relay?
Physically, a common 12-volt relay contains a series of electrical components set inside a small cube or cylinder box made up of hard plastic or aluminum.
You'll see relays with 3 or 4 pins often, but others with 5 and 6 terminals are not unusual. These automotive relays come in different sizes and ratings. And you'll find them under the hood inside the "block" or "power distribution center" box; inside the cabin, in fuse boxes under the dashboard; behind kick panels, and even mounted by themselves.
They switch power on and off circuits around the transmission, engine and accessories like the fuel pump, the headlights, the brake lights, the wipers and horn.
A common electromechanical relay.
|
II. How It Works
It helps to think of a relay as a regular switch, like the
one you use at home to turn on and off the lights in a room.
Why duplicate a simple switching function by having an extra switch inside a box?
Actually, this turned up to be a convenient set up in
electrical circuits. You not only use a small, safer current
circuit — the control circuit — to switch on and off a higher
current circuit — the controlled circuit — but a relay can be
placed in a strategic location to reduce the amount of — and
expenses in — thicker gauge wire needed for high current
circuits.
Testing Relays
|
