Trouble Shooting cruise control

[SpoolingTurbo6]

Ok we have had this truck for 2 years now and my to-do-list is nearing the end. The cruise control has never worked on it, also the brake light
( P. Brake light) is always on ???? Diagnostics shows that the dump valve took a dump Not even sure what that is. Anyone with strange problems like this? I'd like this to work, Is there a way to override this, and what the hell is a dump valve

 

[ItsMyTy]

park brake light always on is probably going to be the switch at the parking brake pedal assembly.

dump valve is probably the vacuum switch mounted on the brake pedal, it could be one of the vacuum valves in the servo.

i would check the vacuum supply to the cruise control servo assembly and the vacuum hose to the brake switch (see if it holds vacuum with a mityvac) and make sure they are ok. check the servo for holes in the rubber boot.