GeoffHeritage

I have fitted one of these to a TD5 and got it wrong first time ,burning out the Kenlowe unit. DO NOT just fit it as in the tdi as you will have problems with the water flow. Kenlowe do an intruction sheet for the TD5 I have one but dont know how to get it to you. Kenlowe I am sure would send you one if you ring them,preheater works well in td5 if fitted properly.This is the diagram if you can read it.

This sounds as if you might have water or even salt water from road gritting in a plug or connector the water will carry enough power to light your lights.I would first try cleaning trailer socket (if fitted) then progress to any other connector that has a live feed to it.Or maybe radio interferance. Geoff