Saturday, October 22, 2011

CAR AC SYSTEM:What is Recirculate?

That mode is where the AC system 'recirculates' the air contained in the car, thru the AC box, over and over, until the desired temperature is reached. The Recirculate button, knob, lever or slide is easily identified by seeing a picture of a little car, with an arrow doing a 'U-Turn" inside the car. This is the opposite of the "Fresh" mode, which is an arrow going 'straight through' the little car icon.

If you are using the "Fresh" mode, you are actually admitting ambient air into the car. Ambient air is much warmer, and makes the AC work harder, and you will see a 10 degree rise in the air temperature from the dash vents. Also, some vehicles admit the 'Fresh' air from under the hood, so, leaving the 'Fresh' mode selected could actually draw in the much hotter underhood air into the AC system.

So, what to do? Anytime you use the AC, please verify that the Recirculate function has been selected. As stated above, this uses the air in the car over and over, and your cooling efficiency will be 10 degrees colder. You can easily check and verify this with an 'instant-read' thermometer. Put the thermometer in the center dash vent, start up the car, turn on the AC, select Recirculate, and watch the temperature drop. It should stop dropping around 34-36 degrees F (depending on humidity, sun load, and a few other things). Now, when the temperature is as low as it will reach, turn off the Recirculate device. You will see the temperature actually rise, maybe 10-12 degrees.

Some additional info: As long as the car is in Recirculate mode, the AC compressor will eventually turn off, when the interior makes the selected temperature. This saves you gas. If you run the AC with the fresh mode selected, the AC compressor runs all of the time. This wastes gas, and costs you more money.

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