Need help with air system.

Have you serviced/ replaced your air dryer cartridge lately?

 

Not sure what your working on... but normally the transmission range, suspension (cab, seat, axles), cab accessories ( air horn, vents, etc), and exacts air supplies run off the secondary air tank, but because they aren’t considered priority they are run off a pressure /check regulator that opens anywhere from 60-90 psi depending on the truck. On freightliners this is usually a Christmas tree looking fitting that has multiple air lines coming out of it mounted on the secondary air tank. If 2 or more minor systems are inoperative, it’s usually because one or more of these valves sticks. On freightliners, there is a button on the end of the valve that pops out when the PSI is met, if you in a bind and can find it, tap on it, or “help” the button pop out.
Hope this helps.

 

Had this problem last year, with the exception that all drives air bags did not aired up. Ended up changing leveling valve. That fixed it. Before changing valve I used to drop the trailer and drove away from trailer and slammed on the brakes couple of times, a quick fix before I fixed properly

 

the only thing all these problems have in common is that they come from the secondary tank all of the air supplies, i would check the check valves in your tanks to make sure that they are not getting stuck also check for major air leaks, you have a side manifold on the chassis its called a safety manifold and the trans and everything you are mentioning feed from there so that would also be a good place to start, driver side of frame by the transmission,

 

Pull the hose from the manifold where the solenoids go and chase the problem from there or feed it with a separate line tin off from the secondary tank not proper but it will work