The starter is supposed to spin when you squeeze the switch and stop when you ease off the pressure. If it runs all the time then its not right. Reversing the leads will only make it turn the opposite direction but try reversing them and see what that does but it probably won't solve the problem. The starter is supposed to turn counter clock wise if you have the starter pointed at the plane nose cone. If you don't mind tinkering, you may be able to pull the starter apart and see whats wrong with the starter switch. It sounds like the contacts are sticking and you may be able to free them up. Good luck.