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Location: Removing a snake out of the neighbor's washing machine
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Quote:
Originally Posted by johnd393
Ok, we know the hot/cold control, and the blend door, has positions in between, that mix the heated and cooled/dehumidified air, right?
The A/C operates on defrost to dry the air. It is not heat alone that demists the windows, it's heated dehumidified air that does it. The A/C has a function in defrost mode besides just to circulate the oil. When it's too cold for the compressor to run, the heated winter air is usually dry enough already.
I've already maintained that the compressor DOES come on when Defog is selected. Defog = inside of windows, Defrost is that little button you press to melt ice from the rear window. It's not that difficult to design a circuit that prohibits the compressor coming on in AC, while allowing it to come on in Defog. It's been around for at least thirty years in cars.
IDK, I was standing at the door smoking a cigarette while my truck was warming up, and it was 8 degrees outside, and my compressor was cutting on and off.
The original purpose of the compressor running in defrost mode is to keep the seals in the system from drying out.
Location: Removing a snake out of the neighbor's washing machine
3,095 posts, read 2,040,736 times
Reputation: 2305
Quote:
Originally Posted by UpstateJohn
IDK, I was standing at the door smoking a cigarette while my truck was warming up, and it was 8 degrees outside, and my compressor was cutting on and off.
The original purpose of the compressor running in defrost mode is to keep the seals in the system from drying out.
And to aid in the defogging process. Which nobody on here wants to believe.
And to aid in the defogging process. Which nobody on here wants to believe.
I'm not going to debate that. I had a Festiva without air that seemed to defog the windshield just fine without a compressor. ONLY car I ever had without AC.
When is is cold outside, the dehumidification process is mostly taken care of by mother nature. Once the cold air flows over a hot heater core, the relative humidity of the air being forced into the vehicle will be very low. The A/C wouldn't have a whole lot of effect because 1.) the air is being heated and, 2.) the humidity is already very low. Besides, automotive A/C systems are designed to operate within a specific temperature range, i.e., the A/C won't turn your car into a freezer; it simply won't be effective under a certain temperature. All running the A/C will do is circulate the refrigerant and system lubricants. This is why newer vehicles actively manage the system under a certain temperature (mostly due to CAFE standards).
Ok, we know the hot/cold control, and the blend door, has positions in between, that mix the heated and cooled/dehumidified air, right?
The A/C operates on defrost to dry the air. It is not heat alone that demists the windows, it's heated dehumidified air that does it. The A/C has a function in defrost mode besides just to circulate the oil. When it's too cold for the compressor to run, the heated winter air is usually dry enough already.
The bolded part is very true where I live. When it’s below 30F the humidity is usually low, so no fog.
I'm curious about this. My AC works, it DOES get cold, it's just winter. So I don't need to use the working AC to get the latent heat and thick, heavy air with moisture out of my cabin and back out to the atmosphere outside the car. But I still run it occasionally to "keep everything circulated and seals lubricated," at least 5-15 minutes a month - including using the AC to defrost the windows when cold - sometimes.
Replaced the compressor that "burnt out" three months ago with a used one. Shop did that a month ago, and refilled system, it does appear to get cold and work good.
This morning, I'm in my 93 Corolla and waiting for everyone to get here. I had the heat on, nice and toasty, helps me sleep. Seems like a cold morning because I'm about to turn it on again. I noticed I left the AC button on the first time, about 20 minutes in.
What exactly happens when I did that?
I don't know about your '93 Corolla, but most newer automobiles use AC when you place the lever to defrost, regardless of where the air temperature is set at. In a lot of automobiles the AC light does not illuminate.
If you turn the AC on while the heater is blowing hot air, it would just be the same as if moving the air-direction control to defrost, except that this time the AC light is on. Automobiles with automatic cabin temperature controls mix hot and cold fresh air as needed to keep the cabin as hot or cold as you want, and still use AC air when the controls are placed to defrost.
Besides that, the AC system operates within certain ambient temperatures. If it is to cold outside, some AC systems are automatically disabled to prevent frost buildup.
I'm not going to debate that. I had a Festiva without air that seemed to defog the windshield just fine without a compressor. ONLY car I ever had without AC.
I'm gonna go out on a limb and say the in a vehicle that does not have A/C the compressor does not come on in defrost mode.
I'm curious about this. My AC works, it DOES get cold, it's just winter. So I don't need to use the working AC to get the latent heat and thick, heavy air with moisture out of my cabin and back out to the atmosphere outside the car. But I still run it occasionally to "keep everything circulated and seals lubricated," at least 5-15 minutes a month - including using the AC to defrost the windows when cold - sometimes.
Replaced the compressor that "burnt out" three months ago with a used one. Shop did that a month ago, and refilled system, it does appear to get cold and work good.
This morning, I'm in my 93 Corolla and waiting for everyone to get here. I had the heat on, nice and toasty, helps me sleep. Seems like a cold morning because I'm about to turn it on again. I noticed I left the AC button on the first time, about 20 minutes in.
What exactly happens when I did that?
The A/C system also dehumidifies. I turn the A/C compressor on anytime the climate control is on. It hurts absolutely nothing to leave it on all of the time. In fact, and this is purely conjecture, I know a few folks who turn the A/C compressor off whenever possible and they seem suffer premature compressor failure.
And to aid in the defogging process. Which nobody on here wants to believe.
They can believe whatever they want, but I've personally witnessed many, many times the benefit of having the A/C compressor on when in defrost mode.
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