I'm pretty sure a government body to protect Australian consumers was not set up to do nothing and have no power to act upon complaints & fraud. We pay their wages so we may aswell support and put them to good use.
A couple of problems I had with dodgy businesses got sorted out quick smart when I mentioned Consumer Affairs. Quite literally on the spot when I said it in front of potential customers! There are legal ramifications involved and potential fines. But more importantly, if you're a business owner the last thing you want is your company image to be smeared or tarnished, resulting in loss of business. In this case, the customer has every right to take the car back and have the problem fixed. If they say 'no', start taking names and their position and subsequently ask for the manager, and if he can't help me, his manager etc etc until it is resolved. Don't ever think it is ok to get f%#@ed over, even by something as trivial (to some) as this.
Good luck