>> then you're going to need a relay that will operate at that voltage.
>> hi,how will that supply the 12 volts to the air horn compressor?
Something like this.
bobsold.goldwingfacts.com/relays.gif
The main problem you've got though is that you need a +12 Volt feed to pin 86, and according to what you've said, you've only got an output of 4½ Volts from the original horn.
Now whether you can get a 4½ volt automotive relay, or something very close, that is also capable of handling the current drawn by the air horn, I've no idea.
Basically though when pin 86 sees a +ve, it operates the relay and links pin 30 and 87 together.
EDIT
The other thing to be careful of, is that some horns are wired up so that the switched feed is negative, not positive.
If this is the case for your car then you'll need to provide a +ve connection to pin 85 as well as one to pin 30. And pin 86 will have the -ve feed going to it from the horn.
You need to establish whether the single wire going to the existing horn has a +ve output or -ve output.
Last edited by: VxFan on Mon 30 Nov 15 at 10:37
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