Air compressor- What is this strange valve for??

I am troubleshooting a cheapie (Meijer sale) home A/Comp which has been working rarely, but well, until today. Now it leaks air as soon as the full pressure has been reached, about 110 PSI, although I have been able to adjust it a bit up to 120 PSI for testing the adjusting screw.

I first thought that the safety valve was sticking, it seemed to be leaking air from its outlet ports, I found some particles inside, probably from the sealant on its threads when being assembled, there was quite a bit of excess. I cleaned it with gun cleaner spray, remounted, and discovered "another" air leak from the same general area, unnoticed before.

There is a tiny valve mounted on the side of the four-port pressure regulator body, it connects to a small copper tube from the tank, and has a tiny pin above the regulator mechanism's armature.

When the regulator shuts off the motor, the armature moves up, the pin is pushed upwards into the valve, opening it against a very weak spring, and releasing the air. I can blow air into this valve orally, and by holding the pin out, close off the air escape. I again tried to flush out the 2nd valve with gun cleaning spray, no improvement.

This valve is actuated now every time the motor is started, and immediately bleeds all the air from the tank. Some air compressor; might be useful by a watchmaker for blowing dust, if he can work fast.

What is the purpose of this valve, and is it possible to get a replacement? My unit is made in (surprise) China. I can order a new (better quality?) four-port regulator, do all come with these valves?

BTW, I must have bought a "good" cheapie, it has a 50% duty cycle! Does the maker think it should be run on a one-minute cycle, or two minutes, or what? Is there a standard time period for the duty cycle spec?

 

the valve is to unload the air compressor when it stops so it doesn't start on a loaded cylinder. there is a check valve between the small copper line and the tank that is leaking.
50% duty cycle means 5 min on 5 min off.

life begins when the kids leave home and the dog dies

 

I think you are totally correct; and, I did not think my cheapie was that sofistickated. I put on a tiny bit of silicone grease on the rubber seal, and will test as soon as the Mrs. gets up Monday AM. Thanks!