Make sure that the selinoid, is a quality one, the good ones are not cheap, and then make sure that it is "square" with the primary mounting flange. Some of the cheap selinoids, have the wrong spacer(the flat bar, with two holes), and if the selinoid is cocked(like us on friday night) off to one side, or un square to the primary, it can hang up and not want to release. I would also check all the linkage and pivot studs on the bendix throwout arm. If they are not "square"(damn, there is that wierd word again) to the pivot point, or if they have been spread to replace the bendix, they can hang up as well. Not to mention, bendix gear alignment to the ring gear. If the bendix hangs in the ring gear, the selinoid can hang up too. Check the rubber boot, behind the selinoid, and make sure it is not hanging on anything, internal or with the selinoid operation. If you still want to find a "Power disconnect" switch, go to any NAPA or good auto store, or a equipment company that sells small equipment and parts. They will either have on, the size of a key switch, or they can order you one. If it is for temporary, get a gate switch, and temporaraly wire it up. Any electrical store should have one, maybe even a Ace hardware.