The good news is that this is going to be a simple one to fix. Most likely it is a loose wire/ connector. You'll need to take the seat and panelling off to find it but if you following the wiring back from the rear light and check that the wire connectors fit tightly. Sometimes the pins inside the plastic connectors work loose so make sure the pins are pushed in fully as well. Dirt can also make for poor connections. You can start from the other end if you prefer, from the faulty brake lever, but either way you should find it easily.
Angela., February 2008
