Bendix AD-IP Air Dryer question..

You're up there where it's cold. Have you checked to make sure that the heater in the air dryer is actually working? Just a thought.

 

Bendix AD-SP Service Data document.

I've found that the first step to diagnosing a problem is to first gain a thorough understanding of how the system is supposed to function when it's operating correctly.

The above document may help, as may THIS one.

 

Since you said the drier will purge, then stop, check a line right quick for leaks that is common to your problem as well as will leak down when truck shuts off. Follow the line from your governor to your unloader on the compressor. Check to verify that neither side is leaking. They tend to melt from the heat at the compressor. I've changed that fitting at the compressor many times due to the line melting inside and leaking. That fitting is less than $10 to change. Takes a 5/8" deep well socket or 9/16" socket if it's the gray colored fitting.

Bypass the drier when you get a chance and that will tell you if you have a drier issue. I am thinking you have the o-ring issue as well.

 

The cover he is talking about is on the top if the comp. cylinder head. You do not have to remove the head itself.
Easy job.

 

Replace it...