trailer air supply problem

Do you have air into and out of the tpv?
If so do you have check valves going to air lines?

 

Been a while but IIRC trailer air is supplied blended air from both tractor primary and secondary reservoirs via a 2 way check valve. Maybe its stuck closed?

 

Goggle Peterbilt air brake diagram. Show the basics of the system. Need to find the air line from dry tank, too red dash valve. Check for obstruction.

 

That check valve thing from NM rings a bell. 78 IHC had three of them next to each other up under the dash. Lost a week of my life to find the that and correct what everyone else crossed up changing valves.

 

I'm having problems that #1 tank is supplied with air but #2 tank stays at 0

 

You should start a new post with your problem and what your truck is posted.

 

I know it’s been 7 years but I’m having the exact same problem. What did it end up being wrong?

 

Suggest you start with BigPerms list of things to check.