How to know if you need new air dryer or just air dryer cartridge?

Why are you asking?

 

https://www.amazon.com/dp/B07L96VTX...abc_WYRQRA5W36ZX4MRKVEEK?_encoding=UTF8&psc=1

Theyre dirt cheap and sometimes less frustrating to replace the whole assembly, buy 2, but make sure the 12v purge is working first

 

It's a maintenance item. Change it yearly before winter. No need to check it, just change it

 

If its a few years old I'd just replace the whole unit. After that I'd just stick a new cartridge on it every fall from then on.

 

Mines doing the same. Blows water from blow gun. That’s definitely a sign. AD9 are cheap enough. I agree with everything already said. I just saw them at Freightliner in Monroeville Ohio for $139. I should have just bought one.

 

Well you answered your own question.

seriously they should he changed every three years unless you have issues with water or running in high humidity areas.

 

It all depends on what year the truck is and what type of air dryer it has on it now? The old type the filter just unbolts and is replaced, the newer type the filters unscrew and have diff. types of medal on the housing and filter and can be like getting a bears jaw apart, and have air lines that control ride hi. of truck and air ride cab and up to 4 other things, and its best to try too get filter off 1st then replace it with a name brand filter, If you can't take it off, pull the hole thing off the truck leaving all hardware in place on frame of truck, and bring the ck. book with you to parts store and be sure to buy a new one not a rebuilt unit air dryer ###.