Got a case 430 with ~500 hours on it. Couldn't get the park brake to disengage a few times and then not at all. Unplugging the lap bar switch and plugging it back in allows me to disengage the park brake. When I plug it back in I hear a solenoid or relay click and can unlock the park brake. I've checked continuity on the switch itself and it appears to work fine but have to unplug and replug every time to get park brake off. What else could be causing this problem?
The lap bar switch may check out good with an ohm meter but not let enough current go through it to everything engaged. The front left relay down in the fuse compartment is the interlock relay for the park brake. It has the "padlock" icon on the decal. You can make a jumper wire to go around the lap bar switch to check if the switch is bad and then replace it if it's bad. You can get the relays at any parts store, just take the old one with you so a parts guy can look at it.