I have a 1998 Ford Expedition and the rear passenger blinker/stop light are not working. The front blinker blinks fast as if the bulb was out but I have replaced the bulb and verified that it is good. I have also replaced the socket and tried both the bulb and socket in the dirvers side and they work fine. Nothing has changed in the vehicle. It worked fine on the way to work and then did not work when I went to lunch. It worked again later that evening and then is now not working again. HELP!!!!