Ask an expert

Recently, when we had an ambient temperature of 34 Degrees my Subaru Impreza's air conditioning system failed to run cool.

Seems OK in lower temperatures.

What do you think?

Dave

From the "Ask Jack" archives - 4 February 2011

We expect a lot out of air-conditioning systems particularly in humid conditions and tend to take it all for granted at times.

Vehicle A/C systems do gradually deteriorate due to the escape of refrigerant. This is a normal condition much like a car tyre loses air pressure over time. The loss of gas will mean the system needs to work a lot harder to drop in-cabin temperatures or could mean in extreme heat, it simply cannot pull the temperature down to the desired level.

So the first recommendation would be to get the system checked out by a A/C specialist and 'topped up' and checked out as required.

Those who only use the A/C at times are at greater risk of having the performance deteriorate more quickly. When the system is not in use, the various seals designed to trap and hold the gas, tend to dry out which can result in the refrigerant leaking to the atmosphere a lot easier.

An A/C system which is constantly in use does tend to lubricate the seals and therefore contain the gas for longer.

There are many different theories as to when and how you should use the A/C. For me, I never switch it off and off-set any increase in fuel consumption by trying to drive as smoothly and as fuel efficiently as possible.

I also believe driver comfort contributes greatly to fuel efficiency and safety.

A couple of operating tips:

* In very hot conditions don’t run the fan speed on maximum. Instead run the fan on a lower speed which provides time for the air to be cooled rather than almost force hot air over the evaporator.
* Make sure you keep the system on internal circulation rather than consistently dragging hot air into the cabin.