Not getting air in reservior of air brakes?

Answer 1

if the governor is regulating the compress and its compressing like it should thn your best bet if you already havent tried this is check the air lines or one other possible thing could be a slice or a hole in the tank itself

Answer 2

Which reservoir are you talking about? Are you talking about the brake chambers themselves, are you talking about the air tanks? Disconnect the discharge line which runs from your your air compressor to your air dryer. With the engine running, hold your thumb over the discharge port. If you can effectively keep your thumb over the discharge port without it being forced off, the compressor output is weak, and needs to be diagnosed.