This Westfalia 13 pin towbar wiring kit is bespoke plug-in for all Alfa 159. The connections are designed to plug directly into the vehicle's connections without any soldering. It comes with the secondary harness required to make the charge connection to the vehicle's fusebox. There will be no CANbus errors and it is MOT friendly. 
 I sourced this abroad as there were none in the UK. I had to find the two harnesses separately and source the instructions which I have included. Overall this cost me well over £400. It was intended for a car that I ended up selling before I had the time to fit it, so it is in unused condition.
This MUST be fitted by a competent auto electrician. It requires the removal of interior trim on both sides, front to back. It will probably take more than a day to fit and you will need to drill the car body in places.
 I DO NOT take returns! DO NOT BUY IF YOU DO NOT UNDERSTAND THIS.