ProStar Sleeper Suspension Modification...

[Nilao]

Make sure you have air coming from the supply line into the leveling valve on the cab. If you have air coming in you should have air coming out when the leveling valve is in the down position.

Do you have air to the seats? I ask cause the seat air shares a port with the cab air bags and if the secondary cutoff port check valve has rusted shut from moisture then you will need a new aid dryer assembly.