Originally Posted by ermracing
Check the adjustment on that brake (and the others). Could be that the S cam flipped over, but I don't recall if that causes them to lock up or not work. Could also be a failed air can. The air brakes are designed to stay locked on when they fail.
My first question is air or hydraulic brakes. Hydraulic brakes can lock up, typically from an internally collapsed rubber hose, or a seized caliper.
When air brakes "Cam-Over" it does not lock. In fact, there's no braking action at all! (This is why it's a really Bad Thing.) There are *NEVER* parking brakes on a steering axle, the logic being you still need to be able to steer and control the vehicle even if a "can" fails while you're driving (it can happen).