On my car the rear fog light only works on Dipped beam not Main.
Mine is the same. I use it once a year at MOT time when I sit in the car and drive the switches and brakes, the lads at the local garage I use are built to last with giant feet.
2009 4/4 Henrietta 1999 Indigo Blue +8 2009 4/4 Sport Green prev 1993 Connaught Green +8 prev