Dumb Defroster Question
00GTP4ME
11-19-2009, 09:29 PM
Ok, this is going to sound really dumb, but I seriously have no clue how this works. I heard that when you turn on your defroster, the A/C is on to dehumidify the air. Is that true? How does the air stay hot if the A/C is running too? This concept is completely losing me, so if someone can explain it in small four-letter words (just kidding) that would be great. :screwy:
tblake
11-19-2009, 10:17 PM
The AC isn't on per say, the compressor runs. I'm not exactly sure how it works, but for defrost it doesn't compress as much freon as in AC. (I think anyways). Look up the GM V5 compressor.
MagicRat
11-19-2009, 10:48 PM
Ok, this is going to sound really dumb, but I seriously have no clue how this works. I heard that when you turn on your defroster, the A/C is on to dehumidify the air. Is that true? How does the air stay hot if the A/C is running too? This concept is completely losing me, so if someone can explain it in small four-letter words (just kidding) that would be great. :screwy:
When the defroster is on, the air ducts arrange themselves to pass the incoming air through the AC evaporator, which cools the air.
As the air is cooled, it's 'dew point' decreases. The excess moisture is removed from the air in the form of condensation, which drains off the evaporator.
Click here for more info (http://en.wikipedia.org/wiki/Dew_point)
This means the air is now drier, but cold. Then the air passes through the heater core where it is warmed up. So now you have hot, dry air that is directed on the windshield.
Usually, this makes a big difference in the speed of the defrosting on warmer days. A defroster without a working AC component often takes a lot longer to clear up a foggy window.
Of course, in a real, cold winter's day, the outside air is already very dry and cold, so the AC is not needed and usually does not switch itself on.
When the defroster is on, the air ducts arrange themselves to pass the incoming air through the AC evaporator, which cools the air.
As the air is cooled, it's 'dew point' decreases. The excess moisture is removed from the air in the form of condensation, which drains off the evaporator.
Click here for more info (http://en.wikipedia.org/wiki/Dew_point)
This means the air is now drier, but cold. Then the air passes through the heater core where it is warmed up. So now you have hot, dry air that is directed on the windshield.
Usually, this makes a big difference in the speed of the defrosting on warmer days. A defroster without a working AC component often takes a lot longer to clear up a foggy window.
Of course, in a real, cold winter's day, the outside air is already very dry and cold, so the AC is not needed and usually does not switch itself on.
00GTP4ME
11-19-2009, 11:27 PM
That was a fantastic explanation, thank you! So on our cars, if we hit the "ECON" button, would that force the A/C compressor to stay off?
JonJon68
11-20-2009, 08:27 AM
Not a dumb question what so ever. I think many people are somewhat confused about this...Including me. Good question..Great explanation.
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