4 Pin and 5 Pin Relay Function (Plus Circuit Picture)

4 Pin and 5 Pin Relay Function (Plus Circuit Picture) – In the electrical circuit of our car, we are very familiar with the relay. So do you fully understand what a relay function is, how does a relay work? In this article, we will discuss in as much detail as possible how 4-pin relays and 5-pin relays work.

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4 Pin and 5 Pin Relay Function (Plus Circuit Picture)


The function of the relay is as a bridge between the current from the battery directly to the mass. The use of relays will cut the flow of electric current that passes through the circuit to reach the load. That is, the relay will make the flow of current simpler and more concise. As a result, the resistance that occurs in the electrical circuit will be smaller so that the use of electricity can be more efficient and the electrical load can be maximized in performance.

The relay works like a normal switch. However, the electromagnetic scheme will drive this switch, while the main scalar will drive the electromagnetic presence. In this case, the switch in the relay will connect the current directly from the battery to the electrical load. Thus, the large current from the battery does not need to cycle through the switch located on the dashboard.

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Almost all car electrical systems use relays, for example in a series of lights or horns using relays has been proven to make the lights brighter and the horn sounds louder. We can modify this to make savings in electricity consumption so that the level of fuel economy will also have an effect.

In general, a relay has 4 terminals, including;

  • Pin number 30, is a provider of current from the battery.
  • Pin number 87, is the terminal connected to the electrical load.
  • Pin number 85, is a signal from the main switch to determine when the relay works.
  • Pin number 86, is the mass of the solenoid that is installed in the relay.

Of the four terminals above, there are relays that have the characteristics of NO (normally open). This type of electricity will be cut off when the relay is off. And the characteristic of NC (normally close) is that the current circuit is connected when the relay is off and this circuit will be disconnected when the relay is working.

Relay More Than 4 and 5 Pin

Based on the number of legs or terminals, relays are also experiencing development. There are at least 5 types of relays based on the number of terminals, among others.

  • 3-pin relay, this relay has three terminals, including terminal 30 as a current source, 87 as a load connector, and 86 as a control relay. While terminal 85 has been connected to terminal 30 in the relay, for relay performance regulation, it is carried out from the mass control of terminal 86 relay.
  • 4-pin relay, the relay on which this relay is based is in a single load electrical circuit such as the horn and fog lamp. This relay has power control from terminal 85 to set when the relay is on.
  • 5-pin relay, this relay is actually the same as a 4-pin relay, except that there is terminal 87a as the second output, in other words, there are two outputs on this relay. This allows a circuit with multiple loads to be run through a single relay. Examples of this relay are in the headlamp (low and high) circuit, and the stop lamp (tail and brake).
  • 8-pin relay, this relay is rarely found in car electrical circuits. This relay allows there to be two switch commands on a relay.

How Relays Work On Electrical Networks

In this section, we will discuss how relays work in electrical circuits.

1. 3-Pin Relay.

The control on the 3-pin relay is located on terminal 86 which should be grounded. Indeed, terminal 86 is connected to the mass, but before touching the mass, electricity will flow to an electrical switch.

For example, in the horn circuit, the current from the battery enters terminal 30 of the relay. In terminal 30 currents will be channeled to the relay contacts and to the solenoid located under the contacts. The output of the solenoid, i.e. terminal 86, is connected to the horn switch in the cabin, only then the circuit is connected to the mass.

If the horn is pressed then terminal 86 is connected to the mass, which will cause magnetism in the solenoid. The magnetism will attract the relay contacts so that terminals 85 and 87 are connected.

2. 4-Pin Relay.

4 Pin and 5 Pin Relay Function

For 4-pin relays, it is usually used for positive control in single-load electrical circuits. For example, in the fog lamp circuit, the current from the battery enters terminal 30 of the relay and is connected to the relay contacts. On the other hand, the foglamp switch will send current to terminal 85 of the relay, and terminal 86 of the relay has been grounded by default.

So that when the fog lamp switch is turned on it will create a magnet in the solenoid which attracts the relay contacts so that terminals 30 and 87 are connected. And the result is the flow of electricity to the load in this case the fog lights.

3. 5-Pin Relay

4 Pin and 5 Pin Relay Function

On a 5-pin relay, there are two outputs. Output 87a will be connected to terminal 30 of the relay when the relay is off, it makes when there is currently flowing to terminal 30 then terminal 87a will also flow current. Usually, in this circuit, terminal 30 is not connected directly to the battery but there are other controls such as the effect of ignition.

Let’s take the example of a stop lamp. When the switch is turned on, a current will flow from terminal 30 to terminal 87a so that the tail light is on.

When the brake is pressed, terminal 85 will send current to the solenoid so that magnetism occurs and changing occurs, the contact on the relay moves from 87a to terminal 87 due to the magnetic pull of the solenoid. This makes the current flow alternately through terminal 87, terminal 87 will directly connect the current to the brake light which has brighter light.

Thus a complete article about the circuit and how the 4 and 5-pin relay works, hopefully, can add to our insight and be useful for all of us.

Why Should You Use Relays? (4 Pin and 5 Pin Relay Function)

Why should you use relays in most electrical circuits? This time we will discuss it by presenting an example in a case. This happens a lot and a lot of questions for automotive lovers, both two-wheeled and four-wheeled. Here is the reason we use relays in electrical circuits.

Usually, for long-distance touring needs, club boys replace the factory default horn with an aftermarket horn. It give sounds louder and louder. They usually use a snail model horn. This horn model does produce a higher sound than other types of horns. So many drop their choice of this type of horn.

Well, when replacing aftermarket horns, you must also use additional relays other than the relay from the manufacturer. What is the reason?

If you replace the aftermarket horn, you must also install a relay, so that the battery power remains stable. Aftermarket horns have more power, of course than standard horns.

The purpose of installing the relay is to maintain the stability of the electric power from the horn. So the use of electric power is not too big and the battery becomes more durable. Usually, people use transparent ones, so that when the relay is damaged, we can see the coil inside. We can easily determine whether the coil is in good condition or not. To add or replace a snail-type horn, we recommend using a relay that has 12V (Volt) and 30-40 A (amperes) specifications.

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