What does pin 30 on a 12V relay do?

Pin 30 is the High Power Feed — it receives fused power from the battery positive terminal.

What is the difference between relay pins 87 and 87a?

Pin 87 is the High Power Output on the Normally Open contact, while 87a is the High Power Output on the Normally Closed contact.

Which relay pin is the trigger wire?

Pin 86 is the Relay Coil Feed (Trigger Wire), fed from the switch in this diagram.

Where does relay pin 85 connect?

Pin 85 is the Relay Coil Ground and connects to ground (-).

Is a fuse used in this relay wiring setup?

Yes, the diagram shows an inline fuse between the 12V DC battery positive terminal and the rest of the circuit.

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12V 5-Pin Relay Wiring Diagram - Pins 30, 85, 86, 87, 87a Explained

Relay wiring sample: switch, 5-pin relay (30/85/86/87/87a), inline fuse, 12V battery

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Wiring diagram showing a switch, inline fuse, 12V battery and 5-pin relay with terminals 30, 85, 86, 87 and 87a labeled to a device.

AI caption November 2020 · Photo 63 of 63

This document is a generic 12-volt automotive relay wiring sample diagram, branded by EPAuto. It illustrates how to wire a standard 5-pin relay (terminals 30, 85, 86, 87, and 87a) with a toggle/rocker switch, an inline fuse, a 12V DC battery, and a powered device (labeled 'To Lights / Accessory etc.'). The diagram shows the battery positive feeding through a fuse to relay terminal 30 (High Power Feed) and to the switch, which supplies terminal 86 (Relay Coil Feed / Trigger Wire). Terminal 85 (Relay Coil Ground) and the device's return are connected to ground (-), as is the battery negative. Terminal 87 is the normally open contact that powers the device when the relay is energized, while 87a is the normally closed contact. A legend at the bottom defines each relay terminal: 30 - High Power Feed; 85 - Relay Coil Ground; 86 - Relay Coil Feed (Trigger Wire); 87 - High Power Output - Normally Open Contact; 87a - High Power Output - Normally Closed Contact. This is a universal accessory wiring reference, not vehicle-specific, useful for anyone adding fused, relay-controlled lights or accessories to a vehicle.

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Frequently asked questions

What does pin 30 on a 12V relay do?: Pin 30 is the High Power Feed — it receives fused power from the battery positive terminal.
What is the difference between relay pins 87 and 87a?: Pin 87 is the High Power Output on the Normally Open contact, while 87a is the High Power Output on the Normally Closed contact.
Which relay pin is the trigger wire?: Pin 86 is the Relay Coil Feed (Trigger Wire), fed from the switch in this diagram.
Where does relay pin 85 connect?: Pin 85 is the Relay Coil Ground and connects to ground (-).
Is a fuse used in this relay wiring setup?: Yes, the diagram shows an inline fuse between the 12V DC battery positive terminal and the rest of the circuit.