Relays are essential components in electrical systems, as they help control circuits with high current loads. One of the most common types of relays is the 87 relay, which is used in a variety of applications. In this article, we will provide a comprehensive guide on the 87 relay wiring diagram, including its functions, applications, and troubleshooting tips.
What is an 87 Relay?
Before we dive into the wiring diagram, let’s first define what an 87 relay is. The 87 relay is a type of electromechanical switch that controls electrical circuits. It is used to switch high-current loads, such as headlights, fuel pumps, and radiator fans. The 87 relay works by using a low-current signal to activate a switch, which in turn controls the high-current load.
The 87 relay is also known as a Bosch relay, as it was developed by the Bosch company in the 1960s. It has become one of the most commonly used relays in automotive and industrial applications due to its reliability, durability, and ease of use.
87 Relay Wiring Diagram
The 87 relay wiring diagram is relatively simple, but it is essential to follow the correct wiring procedure to ensure proper function. The wiring diagram consists of five terminals labeled 85, 86, 87, 87a, and 30.
| Terminal | Function |
|---|---|
| 85 | Ground |
| 86 | Low-current signal |
| 87 | High-current load |
| 87a | Not used |
| 30 | Battery power |
Here is the step-by-step guide on how to wire an 87 relay:
- Connect the low-current signal to terminal 86.
- Connect ground to terminal 85.
- Connect the high-current load to terminal 87.
- Connect battery power to terminal 30.
It is important to note that some relays may have different pin configurations, so it is essential to refer to the manufacturer’s specifications to ensure proper wiring.
Applications of 87 Relay
The 87 relay is widely used in automotive and industrial applications due to its ability to switch high-current loads. Here are some common applications of the 87 relay:
- Headlights
- Fuel pumps
- Radiator fans
- Air conditioning compressors
- Electric cooling fans
- Winches
- Trailer lights
- Horns
FAQs
What is the difference between an 87 and 87a relay?
The 87a terminal on the 87 relay is not used in typical wiring applications. The 87a terminal is a normally closed contact, which means that it is connected to terminal 30 when the relay is not energized. When the relay is energized, the 87a terminal is disconnected from the 30 terminal, and the 87 terminal is connected. In contrast, the 87 terminal is normally open, which means that it is not connected to the 30 terminal when the relay is not energized.
What causes an 87 relay to fail?
There are several reasons why an 87 relay may fail, including:
- Excessive current or voltage
- Overheating
- Mechanical failure
- Corrosion or contamination
To prevent relay failure, it is essential to follow proper wiring procedures, use the correct relay for the application, and operate the relay within its rated specifications.
How can I test an 87 relay?
To test an 87 relay, you can use a multimeter to measure the resistance between the pins. Here are the steps to test an 87 relay:
- Disconnect the relay from the circuit.
- Set the multimeter to continuity mode.
- Touch the probes to terminals 85 and 86, and check for continuity.
- Touch the probes to terminals 30 and 87, and check for continuity.
- If there is no continuity, the relay may be faulty and should be replaced.
Conclusion
The 87 relay is an essential component in electrical systems that control high-current loads. By following the correct wiring procedure and using the relay within its rated specifications, you can ensure reliable and safe operation of your electrical system. We hope that this article has provided a comprehensive guide on the 87 relay wiring diagram and its applications.
