This F#*king horn!

[Mazdabater]

So all I need for my s4 to pass roadworthy so I can register it is to get this damn horn running.

Trouble shooting so far.

Horn button presses in makes relay in CPU click
Wires jumped from GW wire to GR wire no horn
Stop fuse verified good
Battery jumped to green red wire connection for horn - Have horn!

Wiring loom is a bitch to get to lol. During my search I found some people saying the relay is behind the front bar with the rest of them but the diagram says that the only relay is in the CPU which is clicking.

So pretty much with my logic somewhere between the fusebox and my horn there is a broken wire? Or is there something else I'm missing

[Mazdabater]

So got a long bit of wire and connected it to the GR wire that connects it to the horn and ran it back near the CPU so I could check continuity between it and the GR wire coming off the CPU plug and it has continuity. The GW wire measures 12v with a multi meter and when jumpered to the GR wire I get no horn. However when I jump the wire from the battery to the horn it works. The CPU also clicks. So it seems to me like nothing is wrong but I'm still getting no F'n Horn

[Pete_89T2]

Sounds like the solder joints to the connectors on the CPU board are causing the open circuit. Just like the HVAC/logicon/clock & idiot light cluster on FCs, the solder joints like to crap out on these too. If you're handy with a soldering iron, pull out the CPU, open it up and re-do all the solder joints where the connectors join the circuit board. Pop it back in and see if it solves your problem.

[TitaniumTT]

Pete's right, sounds like a few bad solder joints. You could resolder it, I would replace the relay at the same time.

Or de-pin the GW and GR and tap into a 12V (+) and wire up a aux relay.

Or buy a CPU out of a donor car.

[Mazdabater]

Yeah u guys nailed it. Even though the symptoms yesterday were pointing me to a faulty G/W wire I pulled it apart and the solders were all cracked, got one of the avionics guys at work to fix it for me and now my horn works and the car can be registered.

Side note tried to pull the CPU out of my s5 to test it, but the s4 one has a different plug in it. No idea what it could be for possibly the climate control or cruise control as my s5 has neither.