Well it was a little low, I added HWH fluid and it's fine. However! Buzzer still went off. I called RV repair shop and he said those relays are for the automotive not the coach. So I checked everything I could. Then started it, built air and stepped on the brake. Buzzer goes off! Let up and buzzer comes back on also.
Also speedo moves up and down.
Haven't taken it out, but brakes seem to be working and it holds air. I am still