Thorby

Driving along...

I know that all car A/C compressors cycle on and off, that otherwise the little radiator under the dashboard would freeze with the moisture from the environment. Does it cycle on less often if the outside temperature is lower (such as at early spring)? When using the digital air conditioning interface, does the car spend less gas if put on the highest temperature for the A/C?

Since I haven't yet figured out a way to test this by being aware of exactly how much time the A/C compressor is on and also I haven't yet had the time to test how much gasoline is spent on different settings, your theories would be interesting to read.

f550maranello2

iTrader: (2)

u wont notice the difference..

njmaxseltd

iTrader: (19)

All compressors do not cycle on and off. My 99 runs continuously, the pressures are regulated by reed valves inside the compressor. Thats how the R134 refregerent maintains a constant temp and doesn't freeze the evaporator coils. Your 96 does cycle, and yes it's based on pressures as well, which do vary with temperature. So yes it's true that on a cooler day your A/C doesn't work as hard as on very hot days. Thats not to say you'll notice a differance in fuel consumption.

99se5speed

iTrader: (8)

It shouldn't matter what temp or speed your A/C is running at, it still consumes the same amount of gas.

Thorby

Follow up:

I put $10 bucks worth of gas into my empty gas tank. I then drove my car at 90 degree day temperatures (75 night) with the A/C always on set digitally at 82 degrees AUTO. It's really odd but the results when the tank was back at empty were the following: I got 19 miles per gallon, I think the same as I would have gotten without the A/C!

For the naggers and smart alecks: Yes running the AC at this setting DID have a positive effect on the environment inside my car. For a guy like me who is not used to running the AC at all, running it at this setting was much more comfortable than not running it at all.

Maybe the AC is not THAT expensive to use as long as you dont set the temp. to a chilly 60 degrees. I found that being able to drive with the windows closed is really comfortable due to the nice silence and and clean filtered air.

PS: I remind you my car is auto tranny. That affects the city mileage.

Frank Fontaine

Unless I'm mistaken, the only thing that setting your temp above 65 F is that it adds heat. So if you set at 70, you are adding some heat to the air, but it is still dehumidified.

I have a feeling people are trying to apply the fact that at home, you save $$$ when you set your a/c at a higher temp. Because that thermostat does turn the a/c on and off at a set point. Once you go to AUTO on the climate control, your a/c is on.

Thorby

I think I get what you're saying.... but like... only 5% of what you're saying... um... what does defrosting have to do with all this? Dude.. are you like.. drunk or something? LOL I mean.. I just don't get what you're saying.

Frank Fontaine

What I took from your post was that setting the temp to 82 was affecting your fuel economy in a positive way. Would you put it at 100 if you could save more fuel according to your theory?

Who's the one that's been drinking?

pocketrocket

iTrader: (1)

Umm, I thought that the drag/load on drive belts would vary depending on whether the A/C clutch was engaged. I don't expect a vast difference in fuel economy but surely, some?

Thorby

Chucks.

So far I have not come to a conclusion based on your replies.

Anyhow... I have since continued driving with the A/C set at 78-82 degrees so that I just barely get cool enough to be comfortable to drive with the windows up. The mileage has stayed at around 19 miles per gallon city. Outside temperatures have been in the 90's highs and 70's lows (not painfully hot, considering this is a desert).

scrhale

During the Spring-Fall, my car is always at 65. When It comes Winter, I have to play with it constantly to find where I like it. It usually gets too hot in the car when heating it for a little while.

Get excited everyone. Soon we will be driving in healthy cold weather that our cars will all love and generate us those extra few ponies to spin the *&^% out of first and a nice chirp to second.

Jesse729

I think you're right about the Auto climate control adding heat...

All I know is as long as the A/C is on the compressor is always running no matter what it never shuts off. The load the compressor varies depending on the temperature of the evaporator coils and engine RPM, by the opening and closing of the expansion valve. The main difference between a home A/C and a car A/C is the expansion valve in a car can change the pressure in the system. If more warm air passes over the evaporator the expansion valve closes and puts more load on the system to provide colder air, as the coils freeze or the car is at 6000 rpms the expansion valve opens to release pressure.

I don't have auto climate control so when I'm on the freeway on a somewhat hot day i could have the A/C on the first setting, meaning the least warm air passing over the coils, and the car still gets to cold. So i either have to click it to the off position or like the, auto climate does, turn the **** to pass warmer air over the coils which in turn makes the compressor work a lot harder to cool the air wasting more gas.

Thorby

So do you propose that setting the auto A/C at a lower temperature makes the engine work harder? I do see your point but it seems like a very wasteful design to control de A/C temperature by adding hot air rather than by other more economical means.

Ever since I started this post I have continued to use the A/C set at low and I have not had mileage problems. I am not, however, going to try using my A/C at high to test how much gasoline it wastes. I just don't want to get used to being chilly all the time then pooping my pants the day that I don't have A/C.

Wrightsfd

If you first start the car on a warm day (for your 96 model year) the A/C will cycle on and stay on for a long period of time until the desired temperature is reached. Once the temperature (inside the A/C, not inside the car) is reached the A/C will cycle on and off. If you have the temperature of the car set at 65 degrees it will cycle on and off at the same interval as if you have it set at 75 or 85. The only difference is the amount of heat being added BACK to the cooled air. When the ambiant air temperature (the outside) is under 52 degrees, and under 44 degrees the cycle interval lessens respectively. Defrost uses A/C, in both auto CC cars and manual CC cars. I have manual and rarely use my A/C, but I like to have my windows down. On the freeway, or on days above 95 degrees, the windows come up and the A/C goes on. You use less gas with the A/C on and windows up than without A/C and the windows down at freeway speeds.

Haibert88

In the owner's manual of my 96 I30T 5 speed it says that the A/C system of the car does not cycle the compressor on and off, it is on constantly but varies the compressor output.