Its to fool the canbus into thinking all is ok and there are no faults caused by the extra load of the trailer lights.
I'm not sure if its strictly needed on the lingo as it doesn't have a bulb failure warning system. I put one on a 307 and it was quite simple to do as the connections on that unit were marked on the casing.
Hope it helps
05-09-2015, 07:20 PM
(This post was last modified: 05-09-2015, 07:21 PM by Col.)
Because your car is canbus, simply connecting the trailer wiring to the existing lighting circuits can cause all sorts of problems and your lights will take on a mind of their own due to the extra resistance of the extra bulbs. A bypass relay has a live feed (from battery) and ground feed. The power from each of the car lights powers an individual relay in the bypass relay unit. This relay then switches the battery supply to the relavent trailer light ciircuit. The use of the relay doesn't effect the resistance of the car lighting circuit enough to cause a canbus issue.
Hope this makes sence
So is it easy for an amateur to wire, where do I take power from ?.
Yes, quite straight forward. Interior light may be a good source for the power. Check fuse rating first.
Yes easy to fit. Fitted one to my Peugeot 407. I took the permanent live feed directly from the battery. Easily done.
2001 1.9D Multispace.
Diagbox diagnostics in Northumberland.