I replaced the almost unreachable brake light switch with a pressure switch on my '51 Chevy. The switch is on the passanger side frame rail and I replaced a connector with a "T". Brakes bled out and it worked fine. Then started sticking on, so I replaced the switch figuring it was bad, but it's sticking on again. The hydraulic brake system is otherwise stock, with a rebuilt original single pot M/C..

what can be wrong?