my horn has been acting up. it would work for a while then it would stop working but it recently stopped working all together. i assumed that the horn was bad but i decided to try to clean it and give it a try. i cleaned it then hooked it up to a battery and it was working fine then i tried to put it back in the car but it still didn't work. can anyone help?

 

Here's the manual:
http://www.nicoclub.com/FSM/G37/Sedan/2009/HRN.pdf
There are a couple relays, a couple fuses, a couple connectors, the spiral cable in the steering wheel, and a ground all involved. Intermittent operation is the hardest thing to trace but since you know the horn itself is good you should be able to trace back from there and hopefully find the fault.