Just wondering if i can wire up the steeringwheel controls in my au falcon to act as a secondary horn button

Why?

You can never find the horn when you're angry!
I want one here, here, and here!
And they should all play "La Cocharacha"!

Well, if you can't hit the AU horn when you are angry, there is something wrong with you. It is the whole upper section up the air bag pad, unloke the EF/EL, which is 2 pads that are roughly 1 inch square.

To me, it would be a lot of work for little benefit.

That being said, it can be done, but you will lose the controls that you are altering.

To do it to say the audio controls, you would need to pull the airbag off, and fiddle with the wiring for the airbag/horn loom. Once you have the loom out, cut the red/black line, and join it to the purple orange wire. Then the last thing that yoy need to do is to pull apart the plastic that covers the PCB for the Audio controls. You will seee that there are 2 resistors on the PCB - inbetween the Vol+ and the Vol- buttons. Remove these 2 resistors, and connect the 2 points for each with plain wire.

Once you do this, you should be able to use all 3 audio control buttons to activate the horn. Keep in mind that they will never work as audio controls until you reverse everything that you have done.

Another option would be to join the wiring for additional horn switches at the base of the steering column. If you ffollow the wiring down from the clock spring down the column, it will come to a 4 pin connector that is grey. The wires that come off it are black, violet, blue and red/white. any switch that will jump the violet wire to the black one will activate the horn. Just remember that you need to intercept the wires, and not cut them, as any cuts will disable the horn, audio and cruise controls (all of the signals from these items run through these 4 wires).

Hope this helps
Cheers
Chris

yep help heaps just that i have air horns and a bit of a pain wiring into normal horn with two way switches