How to Check a Relay?

[DeVanessa]

Automotive electromagnetic relays serve three main functions: 1) switching, 2) overload protection, and 3) fault protection. The methods for testing automotive relays include: 1. Static testing: Measure the coil resistance and normally closed contact resistance; 2. Dynamic testing: Apply power to the coil and measure the normally open contact resistance. The methods for determining relay condition are as follows: 1. Open-circuit testing: Use a multimeter in resistance measurement mode to check the relay. Set the multimeter to R×100Ω range and verify continuity between pins (85) and (86), and between pins (87) and (87a). The resistance between pins (87) and (30) should be ∞. If the results differ from these specifications, the relay is faulty. 2. Power application testing: If the above checks are normal, apply 12V power between pins (85) and (86), then check for continuity between pins (87) and (30) using a multimeter. If the results don't match these specifications or if the relay heats up after power application, it indicates the relay is damaged.