This is a how-to video for wiring a 5 pin Bosch-style Automotive relay. I’ve created an actual circuit for you to follow along with, and I explain how they work. Relays are important to have for Fuel Pumps, Electric Fans, Horns, Aftermarket Lights, etc. They protect the switch from damage by passing the higher amperage through the relay instead of the switch. In this specific diagram, it is wired as a "positive trigger" relay. That means that you are controlling the positive side of the circuit with a switch, rather than the negative side.

0:00 How to Wire a Relay
0:52 Pin 30 - Power goes into this from the battery.
1:05 Pin 87 - Power comes out of this and goes to your accessory with the switch ON.
1:23 Pin 86 - Power goes into this from the switch.
2:01 Pin 85 - Goes to ground.
2:15 Pin 87A - Power comes out of this with the switch OFF. It doesn't need to be used.
2:36 Relay Diagram Recap

How to Wire a Relay:
Pin 30 – Power goes INTO this pin from a 12v power source (This could be a battery or fuse box). You should always run a fuse in between the power source and the relay. The fuse size depends on what you are powering. See this video to learn about proper fuse sizing. https://youtu.be/EhzN6UdnmPA

Pin 87 – Power will come OUT of this pin. This pin needs to be connected to the power side of your accessory (LED light, fuel pump, radio, etc.)

Pin 86 – Power goes INTO this pin FROM the toggle switch. The other side of the switch should be connected to a power source (A battery or fuse box.) Theres should always be a fuse in between the power source and switch. See this video to learn about proper fuse sizing. https://youtu.be/EhzN6UdnmPA

Pin 85 – This connects to ground. The chassis, body, negative terminal on battery should all work if they are already grounded properly.

Pin 87a – Power will come OUT of this pin when the toggle switch is turned OFF. This pin is not always needed and can be ignored if so.

Relays from the video:
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