I have a 2013 Fiesta with less than 22000 miles on it, the headlights will dim and then go to normal while I increase speed or slow down and sometimes the dash lights will also change brightness with the lights, they do this on both high and low beam. If I maintain a constant speed they will not flicker. They also will not flicker if I'm in neutral and rev the engine and bumps or rough roads also have no effect on this problem with the lights. We normally don't drive at night so I don't know how long this has been happening.