Hi just spent seven months convincing nissan uk and dealer that my tow bar electrics were not fit for purpose. Bottom line was at point of sale I asked for a tow bar with twin electrics to be fitted, no problem except the caravan fridge did not work. As said before took seven months with dealer and nissan uk to get them to accept their smart charge system does not cater for full caravan electrics. They finally arranged to have it modified by a local specialist, works fine now. Buyer beware they are not interested, also got compensation after suggesting the product was mis sold.

Do you have any idea what the specialist did?
I have a voltage sensing relay which cuts out due to the smart charge system dropping the voltage
It's started to 'buzz' when it switches over on load, and so I was looking to fit a new one, but we can hear it dropping out on the road, so I'd like to replace it with a better system if there is one
From your post, I guess the Nissan dedicated kit doesn't work any better?