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Discussion Starter · #1 ·
So I've noticed since I recently bought my 2011 3.8 Track that even when the FAN is just on, no A/C, no defrost, nothing that involves using the A/C, at idle I can hear the A/C compressor clutch engaging and disengaging every few minutes as if it's being used (I can also hear the exhaust note change from the load on the motor).

No car I've owned in the past did this (94 Escort, 97 1.8L ,03 V6, 04 V6 Tiburon). Is it in fact the A/C compressor cycling? If so, WTF? If the A/C button is NOT depressed (or defrost) then it shouldn't be cycling.

My concern is gas mileage. If the A/C is cycling on/off, it's loading the motor and adding additional parasitic drag, therefore lowering my overall MPGs.

I find it strange. Now if I shut the fan off completely, it stops cycling. But I at least like to have some air moving in the cabin while I drive.

Has anyone else noticed this?
 

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If you have the temperature control set to the lowest setting, the system selects "recirc and a/c regardless of any other settings. I learned this from the 2011 2.0t base I had.
 

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Discussion Starter · #3 ·
If you have the temperature control set to the lowest setting, the system selects "recirc and a/c regardless of any other settings. I learned this from the 2011 2.0t base I had.
Yes I did see this but again, obviously the A/C light illuminates when you bottom out the temp to the lowest setting.

What I'm speaking of doesn't matter if I have the temp slighty up or down on heat or cool or even dead center on the temp setting. If I pop the hood, I can hear the compressor clutch engage/disengage from time to time whenever the fan is running, regardless of temperature setting, Auto Climate on or off.
 

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What mode is it in? If you have vent or floor then the compressor should be off with the fan on. Defrost or floor/vent will enable the AC.
 

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Discussion Starter · #5 ·
What mode is it in? If you have vent or floor then the compressor should be off with the fan on. Defrost or floor/vent will enable the AC.
No defrost, no A/C, nothing of the sort.

The mode is usually floor only with temp at around 75-76 deg F. Auto on or off doesn't matter, if I park the car, let it idle, pop the hood, within 2-3 mins I'll hear SOMETHING cycle a clutch and the only thing thats a pulley to my knowledge that has a clutch is the A/C compressor.
 

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You could pull clutch coil fuse or relay or disconnect the pressure sensor to keep it off. There is also a procedure to defeat the AC in defrost mode but I found it still cycles.
 

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when you have the "windshield" vent/defrost on, it turns on the AC without the light turning on.
 

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No defrost, no A/C, nothing of the sort.

The mode is usually floor only with temp at around 75-76 deg F. Auto on or off doesn't matter, if I park the car, let it idle, pop the hood, within 2-3 mins I'll hear SOMETHING cycle a clutch and the only thing thats a pulley to my knowledge that has a clutch is the A/C compressor.
Sure it's not the rad fan cycling on and off?I know it's electric but you'd still hear it.
 

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Discussion Starter · #9 ·
Sure it's not the rad fan cycling on and off?I know it's electric but you'd still hear it.
You know, you might be on to something. lol.

The thing is though, why would the radiator fan STOP cycling once the HVAC system is off though?

What I really need to do is stare at the damn A/C clutch and actually SEE it start spinning.

Could be the radiator fan though and it's just coincidence I'm not waiting long enough to hear it engage after turning off the cabin fan.

IDK. I just haven't had time to do an objective, scientific test on the mystery clutch cycling. I've had more pressing matters to attend to.

Maybe I'll do it during lunch today. My co-workers I'm sure already think i'm weird anyways so who cares if i'm mindlessly staring at my car for ten minutes as it idles.
 

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Alt no. It should be easy to look at the AC clutch face to see if it is spinning or not. Look at it first with the motor off. Then with the motor on, when it's not engaged it should look the same.
 

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The alternator isn't clutched (or is it?).
No, but if the fan is drawing a load while it's running, the alternator will pull a fair load on the engine for a bit. Even my Duramax is noticeable when the alternator kicks in.

Lyle
 

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Revisiting this as here is a procedure to disable the AC when in defrost mode with the Auto Climate Control.

Automatic climate control system
1. Turn the ignition switch to the ON position.
2. Select the defrost position pressing
defrost button ( ).
3. While holding the air conditioning button
(A/C) pressed, press the air intake
control button at least 5 times within 3
seconds.

The indicator on the air intake control
button blinks 3 times with 0.5 second of
interval. It indicates that the defogging
logic is canceled or returned to the programmed
status.

If the battery has been discharged or disconnected,
the system resets to the programmed
defogging logic.
 

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Discussion Starter · #16 ·
To re-enable, just perform again? And by "air intake" you're speaking of the Re-circ./external air button?

This is cool to know and all but it still doesn't solve the mystery of why the A/C clutch engages from time to time when the A/C and defrost functions aren't selected as well as the lowest temp setting and the system is in manual mode.

Now I have noticed since I've posted this earlier this year that it doesn't ALWAYS do it. But I just can't quite seem to make sense of it. Oh well.
 

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It should not engage if it is at the floor or vent setting no matter what the temperature setting unless the temperature setting is at the lowest point this will engage the recirc and the AC as it is the MAX AC setting on the manual climate control.

If you have the Auto Climate Control and have it in Auto then it will turn the AC on when it is programmed to. Using any other mode will cancel this out.

Automatic heating and air conditioning
The automatic climate control system is
controlled by simply setting the desired
temperature.
The Full Automatic Temperature Control
(FATC) system automatically controls the
heating and cooling system as follows;
1. Press the AUTO button. The modes,
fan speeds, air intake and air-conditioning
will be controlled automatically
by temperature setting.
2. Turn the temperature control knob to
the desired position.
If the temperature is set to the lowest
setting (LO), the air conditioning system
will operate continuously.
3. To turn the automatic operation off,
press any button except the temperature
control button. If you press the
mode selection button, air conditioning
button, defrost button, air intake control
button, or the fan speed button, the
selected function will be controlled
manually while other functions operate
automatically.
On my manual climate control in the summer I use to just turn the fan speed off and on to the lowest speed to control the AC compressor when it was not that hot. But have since realized that there is an in car temp sensor so turning the temperature up will not blend hot air and run the AC.

This is not the case with my manual climate control in my 2008 Accent as it does not have an in car temp sensor. It will blend heat and run the AC compressor when you turn the temperature hotter.
 

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I have the same issue, It's the A?C being on. You can tell cause the evaporator under the car will be dripping water. U hate it and set apt at dealer to have it looked at. They said If its on vent and A/C is set to off doesn't matter what temp is set the compressor should not cycle.
 
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