Johnathan
The air dryer on your coach should be as Carl stated a Midland pure air dryer
These dryers are fully repairable / rebuild able
The parts aren't cheap but then neither is the dryer itself
It's best to remove the dryer and work on it on a bench where you can clean it up and inspect for corrosion .
The most common problem is the purge valve leaking which is completely rebuild able using one of the kits from the web site below the dryer cartridge is always a bear to get off but screws on mutch like an oil filter it helps to get it loose while it's still mounted in the bracket on the frame of the truck ( it is the most over looked maintenance item on any truck.)
The three small screws which hold the purge cover on can also be difficult and break off if they are seized a little heat and penetrating oil will help here.
There is nothing had about rebuilding one of these units just make sure to clean any sludge and dirt from all the cavities before reassembly.
The link below will give you the information your need
Hope this helps
Eric
https://www.anythingtruck.com/category/htp-brake-air-dryers-pureairplus.html
