Inside my AC

Discussion in 'General Electronics Chat' started by Nathan Hale, Jul 10, 2013.

  1. Nathan Hale

    Thread Starter Active Member

    Oct 28, 2011
    125
    2
    Hello Everyone, hope all is well. Do you guys know what this "pencil" looking device is inside my Air conditioner?

    Thank you

    CIMG2787.jpg
     
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,795
    951
    It is a 'sensor'.

    I cannot tell if it is for temperature directly or pressure(related to temperature) in telling you how it functions. Similar in operation to a pressure cut out switch as used in automobiles for protecting the compressor from damage when operating under faulty conditions

    Perhaps someone who is more familiar with this equipment can give you a better explanation.
     
  3. DerStrom8

    Well-Known Member

    Feb 20, 2011
    2,428
    1,328
    Judging by its construction and material, I would guess it's a temperature sensor.
     
  4. #12

    Expert

    Nov 30, 2010
    16,345
    6,831
    That's the thermostat bulb. It has a liquid similar to Freon in it so the pressure in the bulb changes with temperature. Look on the back of the thermostat switch and you will see the tube connected there and maybe a bit of crinkling in the case because it is a "bellows", it moves with pressure changes and affects an electrical switch.

    The thermostat is in charge of the compressor. Most air conditioners are wired so it can also turn the fan on and off. Some have an override switch to keep the fan on at all times.
     
    PackratKing likes this.
  5. Brownout

    Well-Known Member

    Jan 10, 2012
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    It's a thermostat. It is filled with gas, and as temperature goes up, the gas expands and at a set point, actuates a switch which turns on the A/C. Sometimes,the thermostat loses it's charge and has to be changed. Your's looks like it's in pretty good condition.
     
  6. #12

    Expert

    Nov 30, 2010
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    Because we have a glaring disagreement, I will clarify. The bulb has a few drops of Freon or something similar in it. This causes a pressure change that is larger than just heating an ideal gas because the gas in the bulb can condense into a liquid, and the liquid can change into a gas.
     
  7. Brownout

    Well-Known Member

    Jan 10, 2012
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    I wasn't really disagreeing. I call it a gas even though it can be a liquid at a certain temperature and pressure. I didn't read your post before making mine. But your'e right, it's actually a mix of liquid and gas. As the temp increases, more of the liquid gasses out and raises the pressure.
     
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  8. #12

    Expert

    Nov 30, 2010
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    We both posted in the same minute, so it's obvious you were typing while I was typing. Both of us were too lazy to go into the minutia of the gas/liquid interplay in the thermostat bulb. I said liquid, you said gas, and I just couldn't leave it at that. Might confuse the customer.

    In 40 years of fixing air conditioners, I have opened a few of these. Sometimes the liquid evaporates quickly and leaves frost on the parts. Some contents remain liquid and smell like mineral spirits. It depends on the manufacturer. These are only used in refrigerators, freezers, and window air conditioners. Maybe in dehumidifiers, I've never fixed one of those. If you see a bulb like this in a central air conditioner, it will be connected to the expansion valve and it is regulating the flow of Freon into the cold coil (evaporator).
     
    JohnInTX likes this.
  9. gerty

    AAC Fanatic!

    Aug 30, 2007
    1,153
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    Just don't put a kink in the line, that would mess up the way the switch works..
     
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