Whether you’re a professional electrician or a DIY enthusiast, understanding how to wire a relay is an essential skill. In this article, we will provide diagrams of 4 pin and 5 pin automotive relays to help you better understand the wiring process. We’ll start with a brief overview of what relays are and why they are important for your electrical system.
Below is the complete guide about automotive relay diagrams such as four and five-pin relay wiring diagrams in easy-to-understand language.
What is A Relay And How Does it Work?
Relays are important in automotive applications because they can help prevent voltage drop, which can damage sensitive electronic components. An automotive relay is an electrical switch, which turns ON and OFF by giving an electrical trigger. It is made up of two circuits, a coil, and high amperage circuit. Each circuit has its pin numbers and wiring diagram.
It is a device that uses an electromagnet to open or close a circuit. When the current flowing through the coil of the electromagnet is increased, the magnetic field produced by the coil increases, which in turn attracts the armature and closes the contacts.
12v Automotive Relay Wiring Diagram
The automotive relay wiring diagram is not complicated, it’s very easy. All you need to know is the basics of a car relay wiring diagram.
Here in this section, I am explaining the wiring diagram of the four and five-pin car relay. Stick with me, here I am giving you a little background about automotive relay terminals.
In the last century, Germany made an organization called DIN Standard. It stands for Deutsches Institut für Normung means the German Institute for Standardization. This national organization gives standard numbers (Known as DIN Standard) to almost every field of technology, covering almost thirty thousand DIN Numbers. The DIN organization also gives a standard DIN code to motor vehicles.
The standard code for electrical terminals is known as DIN 72552 standard and is almost accepted throughout the world. DIN standardizes almost every terminal in an automobile with code. Here we will only discuss the relay’s terminals. Below is the wiring diagram of the four and five-pin car relays.
According to DIN 72552 Standard, each pin of a relay is numbered 85, 86, 30, 87, and 87a.
You need to know that a relay has two circuits, a coil circuit, and a high amperage circuit. In a relay 85 and 86 pins are considered coil circuit pins while 30, 87, and 87a pins are considered high amperage circuits.
Coil Circuit Pin Numbers
-85 and +86 are called coil terminals. Usually, one terminal -85 is given a ground power source and terminal +86 is given a hot power source, to make a complete circuit. A diode is used across the coil circuit in a relay to avoid high voltage spikes.
High Ampere Circuit Pin Numbers
Terminal 30 is considered to be a common terminal. 12-volt power comes to a relay through this terminal (we can say Power-In Wire).
And the second wire of high amperage or current circuit terminal 87 gets power out of the relay and sends it to the component (we can say Power out Wire).
There is also a third wire that comes in the high current circuit of a 5-pin relay, which is called terminal 87a. It is the extra fifth terminal, which is not commonly used in automotive relays. It is used for circuits that need power when the relay is not activated.
4 Pin Relay Wiring Diagram
Car Relay Diagram
In the above four pin relay schematic, there are four terminals, two terminals for coil circuits, and two for high-amperage circuits. The coil circuit’s two terminals are 85 and 86, in which terminal 85 is the relay’s coil negative contact, and terminal 86 is the relay’s coil positive contact.
Similarly, the relay’s high amperage circuit’s two terminals are 30 and 87 in which terminal 30 is a common contact, which means it is an input contact, through this terminal the current goes into the relay whether that is positive or negative depends on the demand of power source.
And terminal 87 is normally open contact and closes when the relay is energized. It is also called an output terminal, which means the currents go out of the relay through this terminal to the component.
5 Pin Relay Wiring Diagram
In a five-pin relay, there are five terminals, two terminals are for the coil circuit, and three terminals are for the high amperage circuit. The coil circuit’s two wires are terminals 85 and 86, in which terminal 85 is considered a negative terminal and terminal 86 is considered a positive terminal.
The five-pin relay’s high current circuit consists of three terminals 30, 87, and 87a. Terminal 30 is a common contact, the battery power comes through this terminal to the battery. Terminal 87 is an open contact and always stays open, and closes when the relay is energized. The power goes out through this terminal to the component when the relay is energized.
Similarly, terminal 87a is a normally closed contact, and its contacts open when the relay is energized. It means, by default, it lets the current out without energizing the relay and stops the current when the relay is energized. It is used on applications where current is required when the relay is not energized.
4 Pin Relay Wiring Diagram For Lights
The above is the circuit diagram for the lights. Terminal 86 wire of the relay’s coil circuit is connected to a hot power source, while terminal 85 is connected to a light switch, which is often a ground power source.
A fused wire comes from the fuse box to terminal 30 of the high amperage circuit, while the second terminal 87 is connected to the headlight. The coil circuit consumes almost 0.5 amp current, which is a not burden on the light switch, as a result, will not burn the light switch.
So, when the coil circuit is activated, the high amperage circuit will make the contact, and the current will directly flow from the fuse box’s battery connection to the lights and the light bulb will illuminate.
4 Pin Relay Wiring Diagram For Horn
The above is the 4 pin relay wiring diagram horn. The relay coil circuit’s terminal 86 is connected to the battery’s positive power source, while negative terminal 85 is connected to the steering wheel horn pad, which is a ground power source.
And Relay’s high amperage circuit’s terminal 30 is connected with fused wire from the fuse box, while terminal 87 of the high amperage circuit is connected to the horn.
Whichever power source (positive or negative voltage) you give to the common terminal of the high amperage circuit of terminal 30. It will output that power to terminal 87 or 87a of a load wire.
For example, if you give terminal 30 hot power sources. In a de-energized state, the relay will power a hot power source to the 87a terminal while in an energizing state it will output a hot power source to terminal 87.
The same goes for ground power sources too.
A Good Way To Remember Relay Wiring Diagram
Some people have difficulties identifying pin numbers and terminals. I use a technique that helps me easily remember the pin terminals.
Usually, relay pin numbers are 30, 85, 86, and 87 (In 4 Pin Relay). Here, just for a while put terminal 30 aside then the remaining terminals will be 85, 86, and 87. Now at this time assume that 85 and 86 are starting numbers in the above terminals and also take the coil circuit of the relay as the initial circuit.
Now link in mind starting numbers represents the initial circuit. It means that terminals 85 and 86 represent the coil circuit. So, whenever you hear about the coil circuit remind yourself that It means terminal 85 and 86.
In this way, you can easily remember coil circuit pin numbers. Finally, the remaining two terminals 30 and 87 are for high-amperage circuits. In which 30 terminal represents a common wire and 87 terminal is power out or load wire.
Using a relay is an effective and efficient way of controlling electrical circuits on low voltage without having to use direct current. A 4-pin relay is typically wired with 2 pins (85 & 86) connected to an electromagnet, one for power and the other to the ground. The other two pins (30 & 87) switch power on a single circuit. There are two types of four-pin relays available, normally open pin and normally closed pin. If you want a normally closed relay, you will want to wire to 87a. If you want a normally open relay, you will wire to 87.
A 12v relay typically has four terminals, labeled 85, 86, 30, and 87. Terminal 85 is for the control voltage (negative contact) and terminal 86 is for the control voltage (positive contact) return. Terminal 30 is for the main power supply (common contact) and terminal 87 is the main power (normally open contact) return. Depending on the type of relay, additional terminals may be available for specialized applications.
Pins 30 and 87 are contact pins that are used to switch power between two circuits. When the relay is at rest, pin 87 is normally open, and pin 87a is normally closed. When the coil is energized using pins 85 and 86, pin 30 connects to pin 87a, completing the circuit.
The difference between 4 or 5 pin relays are as 4 pin relays are used to control a single circuit, while 5 pin relays switch power between two circuits. The 4 pin relay acts as a high-power ON/OFF switch, while the 5-pin relay includes an additional ’87a’ or Normally Closed (NC) pin. The terminals on the outside of both the 4 and 5 pin mini relays provide a good electrical connection, however the fans may not start with ‘key on’ if the relay does not follow the DIN ‘norm’ for pin-out.
The positive pin in a relay is commonly referred to as pin 86. This pin serves as an integral component of the device’s electrical system. This pin is responsible for connecting the normally open and normally closed pins. More specifically, its purpose is to complete the circuit between the control system and the load, thus enabling the initiation of switching operations.
Pin 30 on a relay can be understood as the power supply pin, which is usually connected to battery voltage or other DC voltage sources. This pin provides the necessary operational voltage. It should be noted that while pin 30 may not be utilized in all relays, it is typically found in standard single pole single throw (SPST) and single pole double throw (SPDT) relays used in many applications.
87a on a relay is a designation for the normally-closed contact, which is one of two types of contacts found in relays. This contact allows current to flow when the relay coil is de-energized and it opens when the relay coil is powered up. It acts as a switch, allowing electricity to flow from one point to another when the circuit is in its off state.