Understanding a 4 prong relay wiring diagram is crucial for anyone working with automotive electrical systems, lighting, or even some small appliances. These simple yet powerful components act as electrically operated switches, allowing a low-current circuit to control a high-current circuit. This article will break down the 4 prong relay wiring diagram, making it easy to grasp its function and how to connect it correctly.
The Basics of a 4 Prong Relay Wiring Diagram
At its core, a 4 prong relay wiring diagram illustrates how to connect a relay with four terminals. These terminals have specific functions that dictate how the relay operates. The relay itself contains an electromagnet and a set of contacts. When power is applied to the electromagnet's coil, it creates a magnetic field that pulls a movable arm, closing or opening electrical contacts. This is how a small signal can control a larger electrical load, such as a headlight or a horn. The ability to isolate and control high-current circuits with a low-current signal is the primary reason 4 prong relays are so indispensable.
Let's look at the typical terminals found on a 4 prong relay and their roles:
- Terminal 30 (Power Input): This is the positive (+) terminal where the main power source (usually from the battery or a fused power distribution block) is connected.
- Terminal 87 (Normally Open Output): This terminal is connected to the device you want to control (e.g., a light, pump, or fan). When the relay is activated, power flows from terminal 30 to terminal 87.
- Terminal 85 (Coil Ground): This terminal connects to the negative (-) side of the control circuit. It's typically grounded to the vehicle's chassis or a negative battery terminal.
- Terminal 86 (Coil Positive): This terminal connects to the positive (+) side of the control circuit, usually through a switch. When this terminal receives power, it energizes the relay coil.
Here's a simple breakdown of the operation:
- When the switch connected to terminal 86 is closed, power flows to the relay coil.
- This energizes the electromagnet within the relay.
- The magnetic field pulls the internal contact arm.
- This action connects terminal 30 (main power) to terminal 87 (output).
- The device connected to terminal 87 now receives power and activates.
- When the switch connected to terminal 86 is opened, the coil is de-energized, the magnetic field collapses, and the contacts return to their normal position, interrupting power to the device.
A 4 prong relay wiring diagram is essential for setting up various accessories. For instance, when installing auxiliary lights on a vehicle, you'll often use a relay. The main battery power goes to terminal 30. The lights themselves are connected to terminal 87. The original headlight switch or a separate toggle switch would be wired to terminal 86, and terminal 85 would be grounded. This setup ensures that the high current required by the lights is handled by the relay, not the smaller wires of the original switch, preventing overheating and potential fires.
To see a practical example of a 4 prong relay wiring diagram in action and to guide your own projects, please refer to the diagrams provided in the next section.