How to wire a 4 pin relay | Step-by-Step Guide

Relays are the electrically operated switches that are widely used in electronic circuits these days to control multiple operations. they work according to the principle of electromagnetism to control the internal contacts.

Using relays, a low current circuit can be configured to control high current circuits. this makes them equally beneficial for many applications such as leds, led light bars, automobiles, fog lights, and many other similar applications.

The two main types of relays used are the 4-pin relay and the 5-pin relay. The main difference between 4-pin and 5-pin relays is the number of circuits they can control at the same time. Where 4 pins can control only one circuit, the 5 pin relay is capable of controlling power to more than one circuit at a time.

but, before we continue, please note that we cannot wire a 4-pin relay without knowing the applications. In other words, there is no single way to wire a 4-pin relay.

if you are interested in how you can use a relay for fog lights, bar lights and led lights, please check the linked articles.

Today we will talk about how to wire a 4-pin relay and later on we will briefly talk about how to wire a relay for driving lights.

then, continue with the article and enjoy your reading!

procedure for wiring a 4-pin relay

The image attached below represents the wiring diagram for a 4-pin relay. later we will use this circuit diagram to wire a relay for driving lights.

For the running lights, you will need to connect pin 30 of the relay to the 12v battery with the help of a fuse. here we are not connecting pin 30 with battery directly; rather we are using a fuse. the reason behind this is that the fuse protects us from overcurrents.

In case we are faced with any fault in the driving lights circuit, then the fuse protects the burning lights and other circuits from current surges.

Relay pin 85 is connected to ground, while pins 87 and 86 are switch pins. With the help of this 4-pin relay, you can turn on the headlight bulbs of your driving light by changing the battery connections to either of the circuits connected to pin 86 or 87 of the relay.

why use a 4 pin relay for driving lights

The main purpose of installing this relay system is to keep dangerous voltages out of your cab or driving location. The high voltage that your headlight will need and that is being delivered by the battery is kept within the motor area with the help of a relay.

Basically, you can think of the relay as a switch controlled by another switch. the switch installed in the vehicle’s seat cabin, in front of the driver, works with a very low voltage. look, this voltage is not high enough to damage the controller or other electronic components. this switch is used to power the relay, which is basically an electromagnet. will further control the high current circuit connected directly to the headlights.

this is how a low current circuit controls the high current circuit keeping both the driver and the car’s electronics safe and that’s why we should use a relay in our headlights.

how to wire a relay for driving lights

Let’s briefly talk about the procedure of how to wire a relay for driving lights relay.

1. Identify Headlight Wires: The first step in wiring the high beam relay is to identify the wires coming out of the high beam lights. Normally, there are two wires connected to these lights, one of which is the power wire, usually red, and one will be the ground wire, which is black.

2. connect the wires: now connect the negative ground wire to the vehicle body ground. make sure you make this connection correctly. Also, keep the red positive power lead away from any moving parts of the engine. we will connect this with the relay in the following steps.

3. connect the relay: here we are using a 4-pin relay. The diagram on the side of this 4-pin relay represents all about its connections. but still, if you don’t understand how to connect a 4-pin relay, let’s talk briefly here:

Each of the 4 pins on the relay has different numbers mentioned which you will probably see on the one you recently brought. these include pins 87, 86, 85, and 30.

we will connect the red positive cable coming from the headlights of the vehicle; which we talked about earlier, to pin number 87 of the relay. pin 85 of the relay will be connected to the vehicle body ground.

pin 86 is the wire that will connect to a button or switch that the driver will operate while driving the vehicle.

lastly, pin 30 of the relay that still needs to be connected is what will power the relay. that is, we will connect it with the 12v battery installed in the vehicle with the help of a fuse. but what is the purpose of installing the fuse here?

Here it is mandatory to install the fuse since it protects us from large current surges. it can happen if there is a short circuit in our configuration. therefore pin 30 basically powers the relay and fuse for general protection.

For a better understanding, we present the connections of a 4-pin relay to install the vehicle lights in tabular form.

these are the steps you must follow to connect your relay for running lights. but what about the reversing lights, can we connect them in a similar way? Let’s find that out too!

how to wire a relay for reversing lights

To wire the relay for reversing lights, the same procedure as explained above is used. It is almost the same to connect the vehicle’s headlight wiring relay. the only difference is that pin 87 of the relay is connected to the positive of the reversing lights.Â

We have presented the relay connections in table form for the reversing lights so that it is easy to understand without reading the entire previous section!

Final thoughts!

this is how you can connect a 4 pin relay for driving lights and reversing lights. make sure to carefully follow the guide and connect the correct pin in the correct place. otherwise, not only will you be able to turn on the headlights correctly, but you may also lose the relay!

The key takeaway from this article is that 4-pin relays are wired differently for different applications. there are no set criteria that you can follow. so find your application and connect the relay accordingly!