Pancake compressor regulator valve question

[SBH]

I bought a used pancake compressor and just used it today. When I turned it on, it reached it's peak level and turned off, which I know is normal. Upon viewing the pressure gauge I saw it was dropping fairly quick. My hearing isn't good, therefore, I asked the wife if she heard a leak and she did. I pin pointed the air coming from a hole from the regulator valve which lies under the cap. Therefore, my question, is this normal? I can't imagine it being normal since it continuously turns my compressor on when it falls below the set pressure. I tried turning the valve all the way in and air still leaks. If this isn't normal, is it safe to assume I can replace it?

Thanks for all help.

[JohnnyC]

Not normal. . You can fix the leak using the right parts found at

use some soapy water to find out where the air is escaping.

[Dave Martindale]

It's pretty common for integrated tank-compressor-pressure switch units to have a "switched leak" controlled by the pressure switch. You can tell if your unit has this if the tube that connects the compressor outlet to the tank inlet has a side tube that also goes to the pressure switch, while the pressure switch is mounted on the tank to sense tank pressure. The way this is *supposed* to work is this: when the pressure switch detects low pressure in the tank, it turns on the motor and also closes the "leak". The compressor pumps up the tank to the set pressure, and the pressure switch shuts off the motor. At the same time, it opens the little vent port to let the pressure in the compressor outlet line bleed off. (There is a one-way check valve between the outlet line and the tank that prevents the tank air from leaking). This allows the compressor to start more easily next time, since it's not instantly working against tank pressure.

Now, if you have a pressure switch with this bleeder arrangement, and the check valve leaks, the air in the tank will leak away and the sound of leaking will come from the vent on the pressure valve - but the pressure valve is fine and the check valve is the problem.

On the other hand, if you don't have a vent as part of the pressure switch, and air is leaking directly from the tank through the switch, it's defective.

Dave