Relay Wiring Diagram – As you know that an electrical switch mainly gets used to simply control the high voltage current by which it will only use a specific amount of current only. The wirings of an electric vehicle are in a normal gauge which can’t be able to carry the high voltage current.

It requires a relay to simply manage the high voltage current by simply consuming the least amount of current by which the wirings will stay protected from any type of damage. 

Relay Wiring Diagram

relay wiring diagram

So, if you are willing to master the skill of wiring a car relay by yourself then this article is going to be very helpful for you.

Here in this article, we are going to teach you the skill of wiring a car relay by yourself without any expertise with the practical demonstration of wiring the four-pin car relay for the car lights and horns. 

First Know The Relay Wiring Diagram

It is not a tough task to install a relay if you know the schematics of the relay. Before you install the relay, you need to know about the wiring diagram of the relay. 

At the very first step, we will tell you the four and five-pin relay wiring diagram by which you will be able to understand the relay diagram properly. After this, you can easily be able to wire a relay by yourself. 

Basically, a relay is having four basic terminals which are 85, 86, 30, and 87. A five-pin relay has an extra fifth terminal which is known as the 87a terminal. The coil circuit of the two terminals is known as 85 and 86 terminals where terminal 85 is considered as the negative terminal and gets a ground power source and 86 is considered as the positive terminal which will get the hot power source. 

The coil circuit is one of the circuits which gives the clicking sound when you connect it with the power. So, when you connect the battery power source with the two wires of the relay and it makes the clicking sound then you have to understand that it is the coil circuit. 

Also, a relay is a high amperage circuit which is having two terminals known as 30 and 87 in which terminals 30 is known for the common term which means that the battery’s 12-volt power will come up by the wire to the relay. 

Terminal 87 is one of the power out terminals which means that the 12-volt power will exit from the relay to the component. 

5 Pin Relay Wiring Diagram

There is also one of the fifth terminal 87a which will directly come up from the five-in relay. Also, this terminal is required when the power is needed without using the energizing relay, and also by the energizing relay, the power gets cut off. 

As you can clearly understand by the relay diagram 4 pin and five pin relay and now, we are going to discuss how to wire the relay.

How To Wire A Relay with Relay Wiring Diagram

Wiring the relay is really easy and simple and it is not a complicated task. You can easily be able to wire a relay by your end without any confusion. When you understand the skill of how to wire a 12v horn relay diagram in the card then you can simply be able to connect any of the four-pin relays into the power circuit.

Step 1: Get Prepared

We are going to strip the insulation of the single horn relay wiring

  • First of all, you have to strip one inch of the insulation from the end of all the wires of the relay. 
  • Now, you need to find out the coil and also the high amperage circuit terminals. 
  • Simply check out the relay wiring diagram 4 pin to understand the correct wiring. 

You can simply be able to identify the colic circuit by simply attaching one after the other two wires together with the positive and negative posts of the battery. Also, you will again hear a clicking sound and those two wires are for the relay coil circuit. Also, the other two wires are for the relay’s high amperage circuit. 

Step 2: Make Connections

  • Into the four-pin relay, the coil circuit terminals 85 and 8 will get connected with one terminal of the coil circuit to simply switch and connect with the other terminal with the battery. 

You need to know that connecting the relay’s coil circuit terminals will completely depend upon the empower switch source. Also, if the switch gets the ground power then the relay second terminal is required to get connected with the battery hot power sources. 

  • Now, you have to simply connect terminal 30 of the relay’s high amperage circuit to the power source. 

You need to know that connecting the high amperage circuit terminals of the relay will completely depend on the load of the components. Also, if the component requires the hot power sources then you have to connect it with the battery hot power sources and vice versa. 

  • You need to connect the second terminal 87 of the high amperage circuit with the component quickly. 

Step 3: Tape Into The Wires

You simply have to tap the electric wire to complete this task. Now, you have successfully wired the relay and tape the exposed joints in a careful manner. By this method, you will be able to wire a 12 volt relay to the circuit. 

How to Wire 4 Pin Relay For Lights and Horn

As you know the art of wiring a relay and now, we are going to do the practical demonstration of wiring the four-pin relay for the lights and horn. 

  • How To Wire 4 PIN Relay For Lights
  • How to Wire 4 PIN Relay For Horn. 

How to Wire 4 PIN Relay For Lights

4-pin relay wiring diagram for lights. Below, we are going to share the step-by-step process of wiring the four-pin relay for lights. 

Step 1: Connect The Relay’s Coil Circuit

  • First of all, you have to connect the coil circuit terminal 86 to the positive power source of the battery. 
  • Now, you have to connect the coil circuit terminal 86 to the light switch. 

Step 2: Connect The Relay’s High Amperage Circuit

  • Also, you need to connect a fused wire which will come by the fuse box to the high amperage circuit terminal 30 to the relay. 
  • You have to simply connect 87 of the high amperage circuit to the headlight. 

So, you have successfully finished the four pin relay wiring for light. 

How The Four PIN Relay Works for Horn

The horn relay will start working by simply pressing the steering wheel horn button. The battery-positive power sources will get connected every time with the relay terminal 86 of the coil circuit. 

When someone presses the steering wheel horn pad of the 85 terminal then the relay coil circuit gets energized. This coil circuit will also allow the current to simply flow by terminal 30 of the fused wire from the fusebox of the car horn of automotive relay wiring

How to Wire a Relay for Reverse Lights

In terms of wiring the relay for the reverse lights, the same process will be used. It is the same to connect the wiring relay for the front lights of the vehicle and the only difference is that pin 87 of the relay is mainly connecting to the positive of reverse lights. We are going to share the connections of the relay in the tabular from the reverse lights to simply make it easy for you to simply understand without reading the complete section. 

Pin Number               Connections

87                                Positive Connections from Reverse Lights

86                                Acc of Switch

85                                Ground

30                                12V connection from the battery through a fuse

Why Use a 4 Pin Relay for Driving Lights

The major reason for installing the relay system is to simply keep the dangerous voltages outside of the cabin or the driving area. The high voltage is needed by your headlight which is supplied by the battery and will be kept in the engine compartment by the relay. You have to put a relay into a switch that is mainly controlled by the other switch. The switch is installed into the vehicle’s sitting cabin on the front side of the driver and operates on low voltage. You can simply see that this voltage is not high to harm the driver or the other component of electronics. Also, this switch will provide the power to the relay which requires an electromagnet. 

Also, it will control the high current circuit which is directly connected to the headlights and this is how a low current controls a high current circuit by keeping both the driver and the car electronics safe we really need a relay on our headlights. 


  • What Costs More Than Lower Current Capacity Versions?

The high current capacity wiring and the switches as well. 

  • What Can You Use to Activate One or More Relays?

A single input from one part of the electrical system.

  • How Can You Use a Single Input From One Part of an Electrical System?

In terms of activating one or more replays that complete one or more circuits and carry out the multiple functions from one input signal. 

  • What will Switch Power On For a Circuit When the Coil is Activated?

It is normally an open relay. 

  • What is the Main Purpose of Installing a 4 PIN Relay for Driving Lights?

In terms of keeping the dangerous voltages outside of your cabin and also from the driving place as well.

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In this manner, the horn relay gets wired into your card. Also, I would be glad if you connect with us related to all your concerns about this article on “relay wiring diagram”.

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