Air Dryer Purging Air Every 15 Sec

[GunRunner]

I recently purchased a 2014 Cascadia and had to have some driveline issues addressed and took it to a shop. While in the shop, they were doing a DOT inspection and said that the air dryer is leaking. They replaced the air dryer with a new one and when I picked the truck up, it is purging air about every 15 sec. They thought it was the governor and put a new governor on it and still does it. They then said they found the braided hose was leaking and had a new hose made, still doing it. Next, they warrantied out the air dryer and it is still doing it. They are stumped and so am I. None of these symptoms were present prior to the shop replacing the air dryer. With that said, could it be the unloader valve in the air compressor? That is the only thing that has not been touched. I have researched and searched on here and I am at a loss as to what it could be. Anyone else ever experience this?