Hello Ngoma,
thank you very much for the photo, very helpful. So if I understand correctly, the single wire of the 4th gear connector provide ground for the relay ?
about modifying the circuit : I saw plenty of videos on youtube about that
like :
https://www.youtube.com/watch?v=AxyWeP5Gsxs
But I'm not looking for it
Plus, I was mistaken : I tested the relay, and it doest work (I hope I was choosing the right pins: 31 for ground and 85 for power supply ). I bought it second hand from an old 240 and it lasted like 6 months! So I just ordred a brand-new one.