I have a 5hp sanborn compressor model 500b60v 140psi

by Jim
(Albany NY)

The compressor will run when you first start with no pressure in it. It will run until it gets to its cut off pressure. When the pressure gets down to its start up, the compressor tries to run but does not. It is like it locks up and motor will hum. I then turn it off.

If I drain the pressure down to about 30lbs it will start back up with no problem and will run until it gets to pressure and then does the same thing. Do you know what the problem could be? Please respond to me asap.

Thank You
Jim

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Bill says...

Jim, based on what you've posted, it were my Sanborn air compressor, I'd look to the UNLOADER VALVE. Information on this and the (usuallly) accompanying PRESSURE SWITCH can be found on these pages on this site.

Cheers,

Bill