Question: Does warmer AC = lower fuel comsumption?

Hello

I have had a 2000 Legacy wagon for 2 months now and it is my first car with AC. Which led me to wonder... : Using the AC uses gas (compressed "freon" - not freon, whatever replaced it and is ozone-friendly - takes heat away from air, compressor compresses "freon", takes energy, engine has to work more...). If I put the heat dial, let's say, half way down the blue/cold side, am I using half as much gas for the AC (compressed gas takes less heat away from air, compressor compresses "freon" less to get less cool air, engine has to work less...) or not (compressed gas takes just as much heat away from air, compressor compresses "freon" just as much, takes energy, then air is re-heated, so engine has to work as much...)?

Very important stuff... :)

Thanks in advance

Nicolas

Reply to
Nicolas Dore
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No. the AC works at full capacity and then the cold air is reheated by the heater core.

In cars that have climate control the AC may actually cycle on and off to maintain temperature, but that is not the way the AC works, at least in my '97 OBW.

-- Vic Roberts

Reply to
Victor Roberts

Virtually all automotive A/C units will cycle their compressors to both save fuel (i.e. become more fuel efficient) and to prevent the system from freezing. You can hear, and watch, this happening. I believe that setting the temperature higher will perhaps allow the A/C compressor to be off longer than on, potentially saving fuel. John

Reply to
John A. Mason

It is dangerous to drive for any extended period of time in air recirculating mode. You could die from CO poisoning. The mode should only be used for initial cool down or when traveling through a very dusty area.

-- Vic Roberts

Reply to
Victor Roberts

You are correct that the AC compressor cycles on and off to prevent the evaporator core from freezing. However, on cars without "climate control" I have never seen any evidence that the setting of the temperature control has any effect on the operating of the AC unit.

-- Vic Roberts

Reply to
Victor Roberts

...and whenever I'm approaching the rear end of a Diesel car or truck. Yeah....I usually either open a window or take it off recirc for a minute or so if I'm going long distance...I just didn't get that detailed in my original post.

Reply to
null_pointer

I think people are right in saying that changing your air temp setting will not reduce fuel consumption, as the AC cools the air and then heats it back up. But if you reduce the fan speed, you pass less air over the evaporator and therfore it stays colder longer so the compressor will run less to keep it cool, therfore saving fuel ?

Reply to
Richard Gary Clark

That does make sense.

-- Vic Roberts

Reply to
Victor Roberts

You can open the hood and look at it. It is easy to see when the compressor clutch engages.

-- Vic Roberts

Reply to
Victor Roberts

You should be able to feel it kicking on and off.

-DanD

Reply to
Dan Duncan

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