System Won’t Build Air

[Yauchout]

you should confirm that the main air line going from the compressor to the air dryer is not leaking.. if that truck has a ad-is style air dryer it will fill one tank to 70-90 psi before the other then they will both fill simultaneously. if your primary airline is leaking it may never built enough pressure to fill the other tank... it is designed to prioritize and fill the primary tank first but if you had the lines off it could be miss plumbed not and filling the secondary first