25th-April-08

So, as I take out a selection of cars to test drive after repair, I notice that a lot of the systems have the A/C activated,
but were set to recycle cabin air.

This is a mistake.

A parked car that is unbearably hot needs first to have its windows opened to get rid of excess heat. Then 10 minutes of
recirculation should get the temperature down to a liveable level, at which point, the selector should be turned to the use
of outside air.

Apart from the fact that recycled air can make you very drowsy on a long journey, it is an inefficient way to run an air conditioner,
and is putting excessive loads on the A/C compressor, which is already absorbing as much as 10% of the engine horsepower to
drive itself.

Air conditioning causes a rapid fall off in fuel economy and one of the ways in which its' efficiency can be improved is to use outside
air as much as possible.

You may have noticed that a room air conditioner drips a lot of water outside. This water is known as condensate and is drawn out
of the air as it cools. A window air conditioner uses this water as a cooling medium by arranging to have the fan splash this water back up
into the hot coil.

The same is true of your A/C system in the car. The condensate in the air helps the evaporator, or cold coil, under the dashboard,
increase its' efficiency quite a lot and takes the equivalent load off your engine and A/C compressor.

Other good practices in the efficient use of your A/C system include;
the use of a solar driven ventilation fan attached to the window when you're parked to keep the cabin moderately cooler than it
otherwise might be;
parking in the shade whenever possible;
and the use of a reflective sunshade on the dash board that will not only keep the cabin temperature down, but will help alleviate the
damage that sunlight can do to the plastic materials of the dashboard itself. In the long run, this damage manifests itself as cracks
in the plastic that are expensive  to repair.

Be cool while driving and have a good summer, short as it will no doubt be, in the Great White North.