Contactor Continuity Question

If what you state is correct, then what you observed, ie. (How can multimeter beep with megaohms) can not be true. You must have missed something.

@jack,

you are right. I checked the contactor now. Sometimes shows high and some times low resistance,.

Replace it.

Destroy the old one mechanically so that it cannot be selected for re-use.

In many years of repairing electromotive equipment this problem was common. I would check for a load drop across the contacts. Making and breaking them several times to see if it changed.

You should not rely on the beep, but check the actual resistance.Depending on your set up the are better ways to test than pressing the contactor.

How often does this motor run? How many watts?

Where is the location of the contactor? Protected from weather, mainly condensing humidity?

What voltage is the system?

I've seen contactors on outdoor condensing units that sit over the winter, and then the compressor does not start in the summer. They corrode and even though smooth not damaged contacts, the oxide prevents (in this case 240VAC) to break through this insulating oxide.

As another poster indicated, inspect the contacts for arching damage.

Teeny red ants will self-immolate, like tiny worshippers at the shrine of silver contacts. For some reason they're attracted to the contacts, usually on espresso machines. This was in Key West. Must have fixed twenty machine by simply using a matchbook cover to remove their chitinous remains.

Your continuity meter should only beep at below 100 ohms but it could be faulty so always check what the reading is on the display. Another thing I have noticed when pushing the contactor in manually you can get good readings & when the contactor is pulling in under it's own power the contacts don't make correctly if they are damaged.