How to determine the power relay is good or bad?
1, the relay is composed of two parts: the coil and the contact group, to determine whether the relay is damaged, you need to measure these two parts separately.

2, the coil resistance measurement method.

Using a multimeter ohmic file, place the multimeter in the appropriate resistance block, and connect any of the two pens to the lead pin of the relay coil for measurement.
The test results will be compared with the nominal value, so as to determine whether the coil is open circuit phenomenon; if the resistance value is significantly small, the coil has a local short-circuit fault; if the resistance value is zero, the coil is short-circuited; if the resistance value is infinity, the coil is broken.

3, the contact resistance measurement method.

Use the multimeter ohmic file, with a multimeter 100Ω resistance block, measure the resistance value between the normally closed contacts, usually shows zero a few ohms. If the resistance value of infinity, indicating that the measured between the two contacts is disconnected.
Measure the resistance value of normally open contacts, usually the resistance value of infinity, if the resistance value is very small, indicating that the measured between the two contacts is closed.