AD-9 Leak

Having a little issue with air system. Air builds up to full pressure, governor causes AD-9 to purge as it should, but following the purge there is still air constantly coming out of the purge valve. Pressure in primary keeps dropping down, when it hits low limit the governor reloads the compressor as normal and the leak out the purge valve ceases. Air then builds up normally until the dryer purges again, and the process repeats itself. It seems to me that there shouldn't be any pressure at all to the purge valve once the governor causes it to purge. With the primary pressure dropping as air leaks out of that purge valve, I'm leaning towards it being a failure of the check valve at the bottom of the dryer where the hose exits towards the first air tank. Not really sure how to test that valve without buying a new one and changing it. Can anyone tell me if my logic is sound before I do that? Thanks in advance!

 

I have somewhat ruled out the compressor as it is brand spanking new. Not that a new one couldn't be defective of course. But I'm not sure how that would account for pressure dropping on the primary tank, unless I'm missing something. It seems as if air is leaking out backwards, from the tank and through the dryer.

 

The check valve is still a whole lot cheaper than a reman dryer... and a lot faster to replace. Round here the valve is around $30 and the dryer $150. Neither is going to break the bank. But I want to avoid replacing the valve, only to find out It's something else on the dryer. Or buying a new dryer, and finding out it's something else completely.

 

Well I wasn't going to buy the whole air dryer just for the hell of it... it was replaced a year ago and I had replaced the cartridge just last week. So I decided to put my theory of the check valve being bad to the test. I was going to pull it off and see if it would hold air. As soon as I pulled the fitting for the air tank supply line off, the valve spring and ball fell out and on the ground. No test needed! On went a new valve for $25. Total work time about 10 minutes.