air brakes wont relese

[Robert & Teri Rahn]

I just went to get my bus from its parking spot to bring it nearer to
my shop to attempt replacing the water heater and the air brakes wont
let me move it. When I push in the button after waiting for the
pressure to get up to 120 the brakes stay engaged and the air pressure
starts dropping steadilly untill I pull the button back out. I have
never worked on the air brakes, what is the method for relesing them? I
have the air suspension dumped, does that matter? I have it in a
building that I just built and had to dump it to get it in because the
ground is not level and with it up it almost hits the posts supporting
the building.

Robert Rahn
Kalispell, Mt.
1988 pt 40