dual car horns

[batman]

i want to install a second car horn into my car. the one currently installed has three wires going into it, but the new one i want to put in only has two electrodes. what is the third for?

also, should i disconnect the battery when performing this installation, or leave it connected to test the voltages of the three wires?

thanks!

 

[AdamW]

Perhaps the three wires are positive, ground and switch? The way to test this is with a dc multimeter check if there is a voltage across two terminals without the horn button being pressed.

Alternatively, is it because the alarm and the horn button wire into the horn independently? Way to test this would be with a multimeter whilst pressing the horn button, then with the alarm sounding.

I am not a mechanic and have never worked with car horns, these are just two possibilities I can think of.

Good luck with the new horn, you can never have one too loud

 

[batman]

adamW: i have no keyless entry system nor an alarm, so if it is in fact a switching wire, maybe it's simply not connected to anything.

pauss theau teauh aund kroumpeouts, albert king
we shall dine with the biushoupe

 

[breezer]

seems a lot of trouble to go to, install a wire in a car that isn't connected to anything

 

[batman]

maybe it's for possible aftermarket alarm istallation, they want to have a wire there in case the owner wants that. theres lots of dummy buttons in my car for features i declined to purchase, as well as plastic coverings where fog lights would be if i bought them....

 

[AdamW]

Are there any labels on the wires going into the existing horn? Possibly a daft question, you have probably already checked! But it never hurts to ask.

Follow all the wires and see where they go. If one connects directly to the bodywork then this is your ground. If you can determine this then clip your multimeter negative to this terminal and then check the other two wires whilst getting someone to press the horn button. Set the multimeter to look for voltage, it will be between 10 and 15 volts.

Good luck, I hope this is a Colonel Bogey horn or similar! Loud horns are good, I knew someone with a truck horn in a Peugeot 306, very loud!