Air dryer “extended purge”

97 w900, n14,Cummins compressor, has an ADSP air dryer on it, under normal driving conditions, the compressor cycles about once a. Hour to ever hour an 15 minutes.

rolling back up to the yard on Saturday I notice air guage starts bouncing and hearing that dreaded purge sound, ok, pull into one of our customers large yards out of prying eyes of the NY dept of revenue and its constantly blowing out the valve, compressor on AND off, ok, ive got a new dryer In the side box, toss it on, air back up, and it’s still purging once the compressor kicks it off, though at a lower rate then finally stops after loosing about about 10psi, but does not do it while the compressor is running, I’m now getting 14 minutes out of cycles which is completely unacceptable

I’ve had this problem before but it went away, had a bendex dryer on it and after doing the purge valve a few times I got fed up with it and tossed a TRP ones on which actually solved the problem, since they are 1/3 the price I just figured I’ll replace the whole thing once a year, so I got another TRP one last week, im thinking there has to be some kind of check valve back to the tank, as I’ve separated the compressor and the unloader valve is good and the governor is new and set to 130psi, both the hard line and the exciter line from the governor to dryer are about 2 years old, kind of just thinking out loud in here but welcome to ideas because I want it fixed permanently as the purging dryer drives me nucking futs

Add on: going to pull dryer to tank line Wednesday when I get empty more then likely, both air tanks were 0 this morning after sitting since Saturday night