Hey, I'm having some problems with the electrics on a S111 lightweight - can anybody tell me what the function of the 'filter box' (mounted on top of the rocker cover) is and what it does. when I turn on the ignition the dash light is really dim, if I disconnect the supply to the box the dash light goes to normal brightness!! Essentially, nothing works properly - need help. I have replaced the 2 control boxes (behind the seats) and tried a different dynamo (90 amp)