
The problem is likely to be a faulty switch, or a loose connector. Either way, it should be easy to locate and fix. Remove the seat and look at the wires that go to the rear light. Check all the connections. If all seems ok, look at the switch itself. This will be behind the heel guard, or somewhere near the pedal. pull off the rubber boot, and check the wires. If all seems ok, then get out the multimeter, and check out the switch.