How does a car's blower fan/AC work?

sandyeggosandyeggo
in Cars & Transportation

Hi,

My boyfriend and I are having a discussion about how a car’s blower fan/AC works. We talked to friends and it seems that people were divided on who was right.

My point – When you adjust the speed of the fan to a higher setting, it runs at a higher speed – like a room fan.

His point – The fan runs at a fixed speed and there is a flue/vent that raises and lowers depending on how much air is needed in the car. Now he isn’t talking about the air vents that are on the dashboard, but directly in front of the fan.

He says my argument doesn’t make sense because there would be too much wear on the fan, from being adjusted from speed to speed.

I say his is ridiculous, because a fan blowing at a fixed speed at something that is even partially blocking it would burn out much more quickly.

I’m convinced I’m right, but if any of you can explain how this process works, I would appreciate it. Kudos if you can point me towards a diagram that illustrates this process, not just the AC part.

Thanks!

Comments

  • billrussell42billrussell42

    You are correct. The fan speed switch on your dash is indeed a fan speed switch. It switches in different resistors that reduce the voltage to the fan and cause it to run at the different speeds.

    Changing the speed on a fan does not increase the wear on it. In fact, the slower the speed, the less the wear -- the fan makes fewer revolutions, less wear on the bearings.

    Ask any auto tech or any engineer.

    Search the internet for "resistor bank" fan and you will see lots of examples.

  • andyandy

    When you adjust the fan speed there is a resistor block that determines the amount of voltage to send to the motor..which lets the blower rotated at high med. or low speeds... The flaps in the duct work as diverts.. You have several flaps in the duct some change the direction of air flow ,,floor , defroster, vents,,, and the other adjust the amount of air which flows through the heater core, this adjusts the temperature inside the vehicle....The AC works with the same system but is controlled by a different flap I hope this helps

    Good Luck

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