It sounds like you could seek to enforce your rights under the Australian Consumer Law.
The
ACCC's Consumer Guarantees page provides some useful information on this issue.
Products must be of acceptable quality, that is:
- safe, lasting, with no faults
- do all the things someone would normally expect them to do.
Acceptable quality takes into account what would normally be expected for the type of product and cost.
The remedies you can seek from the retailer who sold you the product include a
repair, replacement, or refund and in some cases
compensation for damages and loss. (You can seek compensation for damages and losses you suffer due to a problem with a product or service if the supplier could have reasonably foreseen the problem. This is in addition to your repair, replacement or refund. But , consumer guarantees do not apply if you misused a product in any way that caused the problem.)
If the air conditioning firm doesn't provide a remedy that you think is appropriate, then here's the ACCC’s
“Make a Consumer Complaint” page that takes you through the steps to follow to make a complaint.
Hope you find that information useful.