How do I stop geckos shorting out my air con?

OPINION: I've got a $3000 problem, and I'm stumped on how to resolve it.

Let me explain:

We have ducted air in our home, and we use it seldom, preferring to cut power usage by using cheap fans or putting on an extra jumper - all in the name of saving money.

However, there are times when it just gets too much and we've used the air to cool or warm us, dependent on the season.

Back in 2012 we had one of those times. It was winter and it was a particularly cold snap, so we decided to warm up just the lounge room.

On went the air and it ran for about 15 minutes before shutting down, with the on/off light blinking to tell us there was a problem.

Next step was a call to the refrigeration people who had installed the machine when the house was built.

The serviceman came along, opened up the outdoor unit and found a few fried geckos in among the circuit boards.

They had short-circuited things and the boards were dead.

About $1100 later the job was fixed with the advice from the service guy to put some mothballs in around the electronic area to keep the little blighters away.

All was well, with the air-con seldom used until a few weeks back when we had a particularly bad spell of cold weather.

On went the air and we had exactly the same problem.

This time the geckos had found an extra circuit board or two and the ensuing bill was more than $1800.

I explained to the lady at the refrigeration place how I had understood the mothballs did the trick.

"Oh, yes they do with the native geckos but not with those pink ones. They don't care about the smell," she said.

"We get a lot of jobs where geckos have done exactly the same thing."

Now, I want to know this: How on earth do I stop it happening a third time?