What is a relay?

A relay is a switch. However, it is actually a switch with two switches in one. In other words, a switch that draws very little current and can turn on or off a switch that draws a lot more current.

When to use a relay?

For example, a small driver-side switch can control the current-hungry headlights. In automobiles, relays are used extensively. It can be used in all the applications where heavy current consuming electric devices are used.

Where are the relays located?

Normally relay boxes are located in the engine room driver side and in the passenger side as well. In addition, there are more fuse/ relay boxes under the driver dashboard and the passenger side glove box.

How do relays work?

Basically, small current switch controls the larger current switch. Small current switchs are normally pin number 85 and 86 connectors. This is the switch used by the automobile drivers. Then, there are pin number 30, 87, 87a connectors. Normally, connector number 30 pin is connected to the battery positive post and it is fused. Relay connector number 87 or 87a can be switched on and off to the device such as headlight, starter motor, window motor, etc.