I bought a 2003 GS430 a couple of months ago. The horn hasn't worked during my ownership. I have checked both the fuse and relay under the hood, as well as the connection on the horns themselves. I swapped the relay with no change but it does click when the horn button is pressed. All of the other buttons on the steering wheel work so I hope it isn't the clockspring. My search only brought up a couple of results but none really came to a conclusion. Any ideas?

Also, the horn for the keyless signal does work correctly.

 

Start simple. Get you a test light and ground it and then pull the plug off one of the horns and put the probe of the test light in there. have someone honk the horn and see if the test light lights up. The fact that you're hearing a click when you press the horn makes me think the relay is working and therefore it's not broken anywhere inside the clock-spring area.

 

Agreed... wouldn't be the first time a Toyota/Lexus horn has frozen stuck. See if the horn is getting ground/power.