help needed air compressor motor

[palumbogio]

Hi! everyone

I need help to diagnose this problem
I have a a 5 hp air-compressor 220 v 21 amp in a dedicated breaker connected by 10/2 wire(1 white 1 black and 1 grey wire) with a manual cut off switch by compressor I check for voltage at the switch, pressure switch, and the motor both the wire are hot and read 120 v each I replaced the pressure switch thinking it my be bad still nothing change so I connected the motor direct on a different 20 amp line with a plug and the motor start and run what I can check to resolve the problem I know the motor start where also can be the problem
Thanks for your time in advance

 

[Howard Sterndrive]

both the wire are hot and read 120 v each

120V compared to where?

They need to read 240 compared to each other. Whether or not you have 240V at the service depends on whether or not the two hots are on the same side of the panel, or opposite sides of the panel, and that is determined by the style of breaker and how it plugs into the panel.

 

[palumbogio]

They read 240v (I meant 120v per cable x 2 )
the breaker is double pole 30 amp

 

[pattenp]

Are you checking the voltage on the load side of the switches or just the line side? If the motor runs when directly connected to power then it has to be a bad switch.

 

[palumbogio]

Checked voltage in both line and both are hot
I hook up the pressure switch to a different 220v source and the compressor vorked as it should I think is the level switch I will make a trip to lowes tomorrow and purchase another one and a new breaker just in case hope this will fix this problem