What is the wiring method of a five-pin relay?
4 Answers
Five-pin relay wiring method: A five-pin relay has two coils, one common terminal for contacts, one normally open contact, and one normally closed contact. The coils are connected to the control voltage. When energized, the relay will pull in, the normally open contact will close, and the normally closed contact will open. The five pins are labeled A, B, 1, 2, and 3. When A and B are not energized, 1 and 2 are connected. When AB is energized, 1 and 3 are connected. Automotive relays consist of a magnetic circuit system, contact system, and reset mechanism. The magnetic circuit system is composed of components such as the iron core, yoke, armature, and coil. The contact system consists of static reeds, moving reeds, and contact bases. The reset mechanism is made up of reset reeds or tension springs.
I remember when I first replaced the car speakers, I had to connect a five-pin relay, that small switching device. It has five pins: pins 85 and 86 are the control terminals, usually connected to the ignition switch or a button, supplying 12V to activate it; pin 30 is always connected to the positive power supply, directly attached to the battery positive terminal; pin 87 outputs to high-current devices, like that new sound system I installed; and there's pin 87a, which is the normally closed terminal—if not needed, it can be left unconnected. Last time, I got the polarity wrong and nearly blew a fuse, but luckily it worked fine after reconnecting—the relay wouldn't operate if the coil pins were reversed. Remember, always turn off the power before testing, and don't let the wires tangle to prevent short circuits. Now, I use it to control various aftermarket parts, avoiding button burnout—it's quite handy.
The wiring of a five-pin relay is quite simple, and it's the same in countless cars I've repaired: pins 85 and 86 are the coil terminals, with 85 connected to the negative or ground, and 86 to the positive side of the switch; pin 30 is directly connected to the positive power supply; pin 87 connects to the load side, such as a fan or headlight; pin 87a is the normally closed output, rarely used. If you're only controlling a unidirectional device, like opening or closing a sunroof, 87a can be ignored. Use thick wires for the connection between 30 and 87, while the control wires can be thinner. I always remind apprentices not to plug them in randomly—wrong connections can cause short circuits, smoke, and even pose a high risk of vehicle fire. Regularly check the relay contacts for oxidation to save a lot on repair costs.
Five-pin relay wiring is both fun and practical: use pins 85 and 86 as control points connected to a switch; pin 30 connects to the battery positive terminal; pin 87 outputs to the device; pin 87a can be left empty or connected to a backup load. I use this for car modifications, like controlling extra spotlights to avoid overloading the original circuit. Testing the clicking sound can help determine if it's working properly. Additionally, many relays have color codes or numbering—refer to the manual for accuracy. Pin configurations may vary slightly between manufacturers, so confirm the model before purchasing and always disconnect power for safety before working.
