Here's a how to I made on another forum
Well obviously you will need a snap off boss (D1 spec etc) and a boss on first ?(momo, nardi etc)
You gotta make sure the boss is all lined up in the correct way so make a wee pen mark or something so you can put it back together at the right angle :thumbsup:
Take the positive wire that comes through your Momo boss and plug it onto the + plug on the Snap off boss as shown below
Also you will notice the negative wire has the plug connecting it to the earthing ring (you may have to bend the earthing ring tab a bit to get the cable plugged onto it) :thumbsup:
Then after that's wired and bolted on, you'll have the face of the snap off boss to do, which is simple to do you snap it back onto the back of the snap off boss so it's in one piece and take one of the wires that comes from the boss, connect it to the positive side of the snap off boss front and plus the other end into your horn button, now test it out :thumbsup:
If it doesn't work then you gotta make sure there are no loose connections and that your shoe horn is connecting the back of the momo boss correctly :geek:
for those with horn buttons that have 2 plugs on them, simple case of elimination, connect a plug to both the positive and negative plugs on the snap off boss front, if it doesn't work then switch the + and - around :thumbsup:
Jobs a good un
Hopefully this helps some folk out, any questions you're welcome to PM me :thumbsup: