1. Measure the coil with the ohmic gear of the multimeter to see if the coil is short-circuited. If the short-circuited coil proves bad.

2. Measuring the normal closed auxiliary contacts with the ohmmeter gauge of the multimeter is not accessible.

3. Press the main contact by hand to see whether the contactor mechanism card is stuck.

4. Power the contactor coil directly to see whether the contactor is suction or not.

5. After the contactor is sucked in, the auxiliary contacts often open are not accessible under the check of multimeter.