will the truck roll? or is it stuck (brakes applied) and wont release the parking brake? also did anyone adjust the brakes? if adjusted backwards it will do as described in prior posting. if I remember right the blue knob will be dead if red knob is pulled and yellow knob is shoved in. to check the control trace the air lines from the emg. port on the air can to the relay valve then find the control port, usually at or near the top remove the control line and then shove in yel. and blue knob should have air in control line if so re attach line and remove one at air can do same thing again and line should have air in line if not relay valve or relay valve air supply faulty.
if truck don't move when brake dash valves are in you may have failed a air can (maxi) and the air to release the big spring is by passing in one chamber and applying the service brake. to check remove a air can air line from the sev. port, push in dash valve you should hear no air if you hear air, do this to each can and then condemn the can with air coming from svc. port. if you have never changed a maxi DO NOT TOUCH! it can kill you find a guy who does!!!!