How to Test if a Relay is Good or Bad?
2 Answers
Methods to test if a relay is good or bad: 1. Without powering the relay, use the resistance mode of a multimeter to measure whether the contacts (output terminals) are conducting. If they are conducting, it indicates the relay is damaged and should be replaced. 2. Use the resistance mode of the multimeter to measure whether the resistance of the coil in the control section meets the standard. If it does not, the relay is faulty and should be replaced. A relay, also known as an electrical relay, is an electronic control device that consists of a control system (also called the input circuit) and a controlled system (also called the output circuit). It is commonly used in automatic control circuits and essentially functions as an automatic switch that uses a smaller current to control a larger current.
I've repaired several cars before, and found that a faulty relay can indeed be quite a headache. Checking if it's good or bad is quite simple: first disconnect the battery to ensure safety, then unplug the relay. Set your multimeter to the resistance mode and measure the two terminals of the coil; the resistance should typically be between 30 to 100 ohms. If it shows 0 or infinity, it means the coil is open or shorted, indicating it's broken. Next, apply a 12V power source to the coil (such as using a small battery). If you hear a clicking sound, it means the switching is normal. Then, measure the contact terminals—they should not conduct when not powered, and should conduct when powered. If there's no response, the relay is definitely dead. It's best to simulate the test in the car to ensure the actual circuit is working properly. Doing it yourself can save some money and also help you learn some technical skills.
