This might have to go to a repairer but might aswell ask here first. I ran my 3hp belt drive compressor for the first time in years to blow wasp killer into the eaves of my house. The compressor was failing to cut out so was either not coming up to pressure or more worrying wasn't cutting out when it should. I had a problem before with the valve in the top of the tank that takes the supply from the compressor corroding and seizing but I seem to remember that being the opposite ie it wouldn't run continuously.That was simply rectified by unsiezing the valve. Unless this is very simple I am going to have to take this for repair, the question is where, I am in SW Herts.
Kevin