Originally Posted by
The Viking
You are in New Zealand, so I assume you are having your cold season now and the system is used to provide heat, yes?
Most likely, the damp patch you can se is condensate that formed on the outdoor coil (that will be an evaporator or cooler now).
If you put some tissue paper down and let it soak up the damp (might be for a couple of hours whilst the system is running), can you set fire to it afterwards? (OK, REMOVE IT TO A SAFE PLACE BEFORE YOU TRY).
If what you can see is oil, it will burn easily, if it's water...