Just hooked my trailer to check my lights before my trip to france on Thursday, the left hand sidelights on the trailer didn't work so first thing I did was check the bulbs and still nothing (bulbs were fine) I then give the wire a wiggle and nothing, unplugged it and went to move my car and noticed the warning on the dash saying tailight out and headlight out.
So I check and my rear sidelight doesn't work and neither does my front, all the bulbs are new as I've just replace then so they are all A-OK! Now to me the sidelight rear is the same bulb as the brake light and it works when I brake? All others are fine apart from the rear and front sidelights so I thought a relay?
I have a little box in my boot not bif 1-2cm wide and 7-8cm in legth with wiring on which is for the tow bar, this has 2 very very small relays on it, theres a tick that comes from here when I put the sidelights on?
Any suggestions welcome - Camping trimp to france means early morning leave on Thursday so would love it to be sorted for then or I can't go

Thanks in advance
Colin!