Reverse cycle A/C - defrost light continually on

[Grumpy John]

Since moving to Tooradin the only source of heat is via a Kelvinator/Electrolux reverse cycle A/C. Not the cheapest form of heating, but until the gas line comes through it's the only alternative.
The problem is that the unit seems to spend an excessive amount of time with the defrost light on and no heat being generated. Is this a maintenance issue that can be rectified, or is it a climate issue (humidity) and I just have to live with it?

[jimbur]

Here's a reply from ignorance John but I've found with the in-laws aircon that cleaning the filter gets rid of most problems.
cheers,
Jim