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Discussion Starter · #1 ·
It seems as if when running in auto mode that the AC button must be pushed and lit for the AC to function.

My question is, When in auto mode with the AC lit does this only give the HVAC system authority to use it when needed or does it keep it running all the time whether its being used or not increasing wear and tear on the unit and decreasing the gas mileage.
 

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FastEddy said:
It seems as if when running in auto mode that the AC button must be pushed and lit for the AC to function.

My question is, When in auto mode with the AC lit does this only give the HVAC system authority to use it when needed or does it keep it running all the time whether its being used or not increasing wear and tear on the unit and decreasing the gas mileage.
The AC compressor in the Murano is a fixed capacity unit and seems to me to operate continuously. Or maybe its just because I cannot tell when its on or off from the lack of a the clutch engagement noise (a click). I hear the click when I first start the car in the morning, but otherwise, even in cold weather it seems the AC is always on.

If you press auto, AC will always turn on with it. Only after that can you turn off the AC manually by pushing the AC button.
 

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Discussion Starter · #3 ·
So its safe to assume that I can just put it on auto and fagedaboudit with no additional wear or loss of gas mileage.

The owners manual offerers no help at all for this.
 

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I've found an audible indication that the air compressor is kicking in - tune radio to a low FM station (i.e., around 88.3 or 88.5 FM) - the stock radio gives a whine through the speakers when the AC compressor is in use (manually turning AC off thorugh the controls removes the noise - turning AC on has it return).

So I would assume that the AC compressor does cycle on/off.
 

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Note that you CAN still be in auto-mode with the AC off. It will still automatically control all the other settings.

I'm getting into the habbit (now that the weather is cooling off) of hitting Auto then AC so that I'm in auto mode for everything but the AC is off. Not yet sure how this affects gas mileage, but I'm hoping to find out.

I know that in my little cars (CRX, Civic Hatchback, Del Sol) that my gas mileage would go up a few points (28 to about 32 in my Del Sol) with the AC off, but I would imagine that it would make less of a difference in the MO considering the amount of weight and the engine size compared to the AC compressor. I wouldn't expect more than 1 or 2 mpg difference max.

Has anyone messed with this to determine an actual difference?
 

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Yes the AC does cycle on and off as needed when the AC is select on (i.e. light on).

I, like gymkid, manmually turn off the AC when the air is dry and cool. It is not needed to run. However to avoid a quick initial power on cycle I try to avoid turning off the AC when turning on the system but rather turn it off prior to turning the car off so the next time I get in it doesn't cycle at all. I realize that this may not make sense but I'm too lazy to clarify.... I understand it in my head and all the voices agree.

:p
 

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Yes I've tried this and the difference is about 1mpg. Not enough in my opinion, to ride around uncomfortably in a stuffy car.
 

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Really only 1 MPG... hmmm.

IMHO its all these small things that help save energy. A single light left on in a house doesn't mount to much but if everyone left one on... you get the idea. If the AC was off in cool dry air for all cars I wonder how much energy/gas could be saved.
 

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The thing that determines when a compressor would kick in is first the inside tempreture, and second the tempreture of air passing over the evaporator unit (A/C radiator inside the car). If your inside tempreture has been reached, there is little cycling will be going on so the A/C usage will be minimal.....just my 2cents...:)
 

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Discussion Starter · #10 ·
Just a little lost in terminology.
If the AC is "Cycling" when in Auto Mode and the AC light is on. That means that it doesn't matter if the AC being used or not its still running in the background waiting to be called upon to do its job.

If in Auto Mode and the AC light is OFF the AC unit is not running.

We get a huge shift in temps here this time of year. Its 49 in the AM when I leave the house and 85-95 in the PM when I go home.

If leaving the unit in fully auto mode with the AC on isn't going to compromise my MPG or add extra wear to the system Ill just keep it there till it cools off. If its hurting me, ill reach over and turn it on or off when needed.

Im guessing this is the reason they don't advertise it as Climate Control.
 

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The light you see on the dash just means power to the system is on. The cycling (actual cooling) is controled via sensoors as I described above.

Having said that, I manually turn A/C off when I don't need it!
 

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Clarification:

When the A/C light is on, the compressor is NOT neccessarily running. It will be controlled by the computer, using the inside and outside temperatures, and possibly humidity as well. The A/C tends to run more when it's raining out, to keep the windshield clear of moisture.

Turning the light off does nothing more than the computer does when it detects that the A/C is not needed. Basically the A/C is OFF or AUTO.

When it's cool and dry, I tend to turn the A/C off, put the temp at minimum and set the fan to medium low to continue bringing in fresh air even while stopped.
 

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From my personal observation you are loosing up to 2 MPG when driving with A/C. Of course it depends on driving condition. I am driving 65/35 (city/highway) and my MPG drop from 17.4 to 16.1 :( while driving with A/C (ambient temperature was 90-100 F)
 

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zebelkhan said:
The thing that determines when a compressor would kick in is first the inside tempreture, and second the tempreture of air passing over the evaporator unit (A/C radiator inside the car). If your inside tempreture has been reached, there is little cycling will be going on so the A/C usage will be minimal.....just my 2cents...:)
As I understand this is not completely true. The compressor will cycle when the pressure/temp of the AC (freon or whatever they use today) system gets low/warm too regardless of the inside temp of your car. So in other words even if you car is at or below he desired temp, the compressor will still cycle.
 

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FastEddy said:
Just a little lost in terminology.
If the AC is "Cycling" when in Auto Mode and the AC light is on. That means that it doesn't matter if the AC being used or not its still running in the background waiting to be called upon to do its job.

If in Auto Mode and the AC light is OFF the AC unit is not running.

We get a huge shift in temps here this time of year. Its 49 in the AM when I leave the house and 85-95 in the PM when I go home.

If leaving the unit in fully auto mode with the AC on isn't going to compromise my MPG or add extra wear to the system Ill just keep it there till it cools off. If its hurting me, ill reach over and turn it on or off when needed.

Im guessing this is the reason they don't advertise it as Climate Control.
No the system is climate control.. that is why you set it at a desired temp and the system will try to maintain it. I
f it is cool and dry and the AC light is on it will run. Soooo if you don't need it turn it off and save gas and wear.

The compressor will never run when the outside temp is below something like ~24F even when the AC light is on. It is simply just too cold for the system to operate.

I hope this helps.
 

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Gonzo

Luck You

We get a huge shift in temps here this time of year. Its 49 in the AM when I leave the house and 85-95 in the PM when I go home.

We get 70 in the morning ( nice breakfast on the patio) but 103F by 3pm in the afternoon.

So we only get a 30F like swing.

However it better than 90 in the morning and 115F in the afternoon
bu a dammsight. Even though the swing is less, I like swings, (High Red Velvet ones best)

Soon it really cold at 60F in the morning and 75F in the afternoon Now that the kind of low swing I like. G
 

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Discussion Starter · #17 ·
I live just on the south west tip of the Napa / Sonoma Vally. We get the High Vally temps during the day then the sea breeze / marine layer the moment the sun goes down till 11-12 the next day. Doesn't matter how hot it is during the day its always between 35-60 at night.

Great weather for Grapes and Real Estate values. Not so good for skinny dipping at night.

I guess I have come to the conclusion that Ill leave it on auto with the AC till the weather is such that I don't need the AC then Ill keep it on auto without the AC.

The 1-2 MPG difference isn't an issue to me. If it were double that I may think twice.

Thanks for all input and clarification.
 
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