This is relay you have.
You can use it to switch negative and keep your original positive wire (civilised sound) or you can switch positive and have horns loud as a bus? which are you looking for. Civilised sound or loud as hell?
for civil sound, use it to bridge negative while using original positive wire.
Cut the horn negative wire
good 12V -ve to contact 3
horn negatives to contact 5
any good 12V +ve to contact 1
horn negative trigger to contact 2
This will allow you to still have the horn fuse stay in service
for loudest sound
cut both horn wires
good solid direct 12V -ve to horn ground
good 12V +ve (fused) to relay contact 3
horn positive pole to relay contact 5
original horn wire +ve to relay contact 1
original horn wire -ve to relay contact 2
to test the sound before cutting - mount the horns, and connect the original positive wire to them, take a piece of wire and and connect it to their negative poles, touch the battery negative or any other grounding point you are choosing - listen to the sound, (this is switched ground - first case above)
to test the loudest - remove the original wiring positive wire and attach another piece of wire to them and connect to battery positive, now touch the negative wire to the battery negative, (case 2 above)
choose which you like and wire up accordingly. I personally like case 1, no load on steering horn contact, and a civilised sound suitable for a passenger car.
