How to Identify a Bad Relay > 자유게시판

Testing and diagnosing faulty relays is an essential skill for anyone working with electrical systems, whether in automotive applications. Relays are simple devices that use a electromagnetic pulse to control a larger electrical load, and when they fail, they can cause everything from a pump that remains inactive.

The good news is that the vast majority of relay faults can be identified with common household equipment and a little patience.

Start by understanding the relay’s role in the circuit. Relays typically have five terminals labeled 30, 85, 86, 87, and 87a. Terminal 30 is the common input, 85 and 86 are the electromagnet pins that receive the trigger voltage, and 87 and 87a are the load terminals. When the coil is energized, the relay switches from 87a to 87, completing or breaking the circuit.

The first step in diagnosis is a physical examination. Look for signs of charring, deformation, or corrosion on the outer shell or terminals. If you see any damage, the relay is likely faulty and should be replaced immediately. Also check the holder the relay plugs into. Loose, or corroded pins can produce false failure symptoms.

Next, use a multimeter to test the relay’s coil. Set your multimeter to measure ohms. Place the probes on terminals the coil pins. A functioning coil should show a resistance between 50 and 120 ohms, depending on the specification. If the reading is infinite or very low, the coil is shorted and the relay needs to be replaced.

Now check the contacts. With the relay disconnected, place the multimeter probes on terminals 30 and انواع رله 87a. You should get a reading of open circuit because, in the resting state, these contacts are disconnected. Then place the probes on 30 and 87. You should also get infinity, as 87 is normally open. If you get a closed circuit here, the relay contacts are welded, which is a irreversible damage.

To test the switching function, you need to energize the coil. You can do this by connecting a automotive battery to terminals 85 and 86. You should hear a audible snap as the relay activates. If you hear nothing, the coil is likely dead. If you do hear a click, immediately check continuity again between the output contacts. You should now get a near-zero ohms, indicating the contacts have made contact. If there’s still an open circuit, the switch mechanism are worn.

Another quick method is the interchange test. If you have a spare relay of the same type, replace the suspect one and see if the system operates normally. If it does, the original relay was bad. This is especially useful in vehicles where relays are readily available.

Always remember to turn off the ignition before handling or testing a relay. And when in doubt, consult the vehicle or equipment manual for the required timing and load ratings. Some relays are designed for high-cycle applications, and using the wrong one can cause system failure.

Most relay failures are caused by aging, excessive heat, or voltage spikes. Regular cleaning and replacing relays at the earliest symptom of failure can prevent bigger problems. Keep a essential spare relays on hand as spare parts, especially if you work with systems that require frequent switching.

Testing relays isn’t complicated, but it requires precision. By combining physical check, multimeter readings, and a practical insight of how relays work, you can quickly and confidently diagnose and replace most relay-related issues.