AC580V thumps and then nothing!

by Logan Roche
(Ellis Grove IL USA)

I have a snap on air compressor model AC580V serial J181945 the worked good until last week and now the motor won't run.

It's not locked up and turns free, but when you turn it on and hit the start it thumps and then nothing.

I have tested the power to it and the power to the motor. I have 240 going to the box where the switches are located but it seems as though I can only get 120 volts to the motor, which is probably why it won't start. Any ideas?

Comments for AC580V thumps and then nothing!

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Nov 23, 2017
120V thump
by: Doug in

It's not entirely clear what you're measuring (120 to ground?) but anyway, sounds like maybe one side (or half) of the pressure switch contacts has failed.

You could try bridging a suspect set of contacts and see if that makes it work.

Or, unplugged, you could check for continuity through the contacts while manually operating it.

Good luck - let us know what you find.

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