Thanks for your reply please can you tell me where I can buy one and what to ask for
Well, to do that id highly recommend you spend the time to study how they work so you dont need to ask, as if youd need a premade wiring diagram theres a good chance of ending up with something that doesnt work.
What i did was take a diagram of the plug i wanted for the trailer, got those labelled into the boot throgh a gromet.
Then i found each wire in the rear lights (left and right) and pulled wires to the same spot in the boot, labelled with where they went to/from.
Took a thick (fused) wire, from the battery, through the big gromet in the top of the firewall ziptied it safely down one side of the car under plastic trim and took it out in the boot.
I made it thick enough that I could run a cigarette lighterplug for a cooling box if i ever feel I need that..
From there i bought a can-bus hitch wirering set for some volvo? From something called biltema. It said all warranty void and danger if modified... So dont do what I did... At least not without making sure you understand any potential dangers and you are willing to take those risks..
In the manual for the relays it said what goes in where and what comes out where with nice colour coding, this is where all the labelling comes in, left blinker in got soldered to left blinker in, in the relay, and the one in the plug by the hitch got the same treatment, ground, fog light, etc etc...
I think the relay was for a 11plug and I wanted a 7, so off with the not needed wires, and done...
Again it might not be worth the savings if you are not comfortable with doing it, as any damage to the car following might negate your savings...
