I recently fitted a new trailer plug and wiring to my 2004 E320 W211 which is fitted with a factory fitted towbar. Everything worked first time with no problems, the trailer was then not used until this last weekend when I plugged in the lights and nothing! Realising later that the plug may have got wet due to it being left in the open I checked the fuses and yes the trailer fuse in the boot was blown. I replaced this and the indicators and stop lamps worked, but no trailer tail lights and the trailer tail light warning is showing on the dash. I have checked for power right down to the cars hitch socket and there is nothing, so I presume there is another fuse blown somewhere. Does anyone know where this fuse is located or have any other ideas about the problem?