Wiring Diagram for 4 Pin Relay: A Comprehensive Guide


Hello readers! In this article, we will delve into the world of wiring diagrams for 4 pin relays. Whether you are an automotive enthusiast or an electrical technician, understanding the intricacies of relay wiring is crucial. So, let’s dive in and explore the various aspects of wiring diagrams for 4 pin relays.

1. Purpose of a 4 Pin Relay

A 4 pin relay is an electromagnetic switch that allows you to control high-power devices with a low-power signal. It acts as a bridge between the control circuit and the load circuit, enabling you to control various electrical components with ease.

2. Pin Configuration

A 4 pin relay consists of four pins: two for the control circuit and two for the load circuit. The control circuit pins are typically labeled as Coil+ and Coil-, while the load circuit pins are labeled as Normally Open (NO) and Normally Closed (NC). Understanding the pin configuration is essential for proper wiring.

3. Wiring Connections

Proper wiring connections are crucial to ensure the relay functions correctly. Begin by connecting the power source to the Coil+ pin and ground to the Coil- pin. Then, connect the NO pin to the device you want to control and the NC pin to the power supply. This configuration allows the relay to switch the device on or off depending on the control signal.

4. Advantages of Using a 4 Pin Relay

There are several advantages to using a 4 pin relay in your electrical circuits:

  • Easy to install: The wiring process for a 4 pin relay is relatively straightforward, making it easy to install even for beginners.
  • Compact design: 4 pin relays are compact in size, allowing for space-saving installations.
  • Reliable operation: With their electromagnetic switching mechanism, 4 pin relays provide reliable and efficient operation.
  • Versatile: These relays can be used in a wide range of applications, including automotive, industrial, and home automation systems.

5. Disadvantages of Using a 4 Pin Relay

While 4 pin relays offer numerous benefits, it’s essential to consider their limitations as well:

  • Limited switching capacity: Compared to higher pin relays, 4 pin relays have a lower maximum switching capacity.
  • Less control options: Due to their limited pins, 4 pin relays provide fewer control options compared to relays with more pins.
  • Not suitable for heavy loads: If you need to control heavy loads, a 4 pin relay may not be the best choice as it has a lower maximum current rating.

6. Alternative Wiring Diagrams

Although the standard wiring diagram for a 4 pin relay is widely used, there are alternative wiring configurations available. These alternatives may provide additional control options or cater to specific circuit requirements. One such alternative is using a diode across the coil pins to prevent voltage spikes and ensure smooth operation.

7. Wiring Diagram for 4 Pin Relay: A Step-by-Step Guide

To help you visualize the wiring connections, refer to the following table:

Pin Connection
Coil+ Connect to the power source
Coil- Connect to ground
NO Connect to the device to be controlled
NC Connect to the power supply

8. Frequently Asked Questions (FAQ)

Q: Can I use a 4 pin relay to control AC devices?

A: Yes, you can use a 4 pin relay to control AC devices as long as the relay’s specifications match the requirements of the AC circuit.

Q: How do I determine the maximum switching capacity of a 4 pin relay?

A: The maximum switching capacity is usually specified in the relay’s datasheet. Make sure to check the datasheet or consult the manufacturer for accurate information.


In conclusion, understanding the wiring diagram for a 4 pin relay is crucial for effective control of electrical devices. We have explored the purpose, pin configuration, advantages, and disadvantages of using a 4 pin relay. Additionally, we discussed alternative wiring options and provided a step-by-step guide for easy understanding. By following the proper wiring connections and considering the circuit requirements, you can harness the power of 4 pin relays in your projects. Happy wiring!