Took my E220 for MoT, passed on everything except rear fog light! Bulb is good, fuse is good, and the indicator light on the switch in the cabin illuminates when switch is pulled out. But there is no current at the wire at the rear panel... (tested with multimeter). I realise there must be a fault in the wire somewhere, are there any obvious weak points where failure is likely eg where the wire enters the boot? Many thanks for any advice. PS post-MoT, I was looking at the problem and the bulb suddenly started working again! This morning I was all set to go back for the re-test, when a final check showed it had failed again! Very frustrating.