Ok....my 3.5 SL doesn't work that way. I can CLEARLY hear the compressor's "clutch" engage when in AUTO (which I always have my system set to) and upon pressing the "AC" button. This is also doubly confirmed by a momentary change in the tachometer at the moment the "AC" is pressed.....and again when the "AC" button is pressed again.
The belt that powers the compressor is always turning the compressor's pulley .....but it's not until the "AC" button is lit that the "clutch" engages and actually powers the compressor.
Again perhaps you have a problem if your car doesn't operate that way.....again I have a 3.5 SL
Glad your operates like that, but mine and apparently many others does not. Mine is also a 3.5 SL. I'm well aware of how to tell if the compressor clutch is engaged - I've done considerable work on auto a/c systems.
I'm not too concerned about it as it's easy to press the AC button twice to turn it off.
But it's always on when auto is first pressed - regardless of what the AC light says.
Well....my dealers technician confirmed to me that the compressor is NOT ON unless the AC is ON......and if the indicator light on the AC button is lit then, and only then is the compressor ON......otherwise the compressor is off.
Why would they design a system where the mpg robbing compressor is always on, when they are trying to achieve maximum mpg........????.....obviously, they didn't .
rob,
The technician sold you a story. Believe me and dbc, not him.
Why would they design a system this way? Easy. They dropped the ball. They didn't complete the vehicle testing program before they sent the product to production. Every product has bugs and this is one of them. I've been a test engineer for 29 years and inexcusable bugs like the one under discussion happen when schedules take priority over the engineers' wishes. It's not unusual. Even cursory testing would have uncovered this anomaly.
Here's an experiment that will convince you, if you're open to being convinced. Tomorrow afternoon, start the car and set the temperature to 90 (highest setting) in auto mode. Let the car get real hot. Now quickly set the temperature to 60 (lowest setting), remaining in auto mode. The AC light will remain off. Now, feel the air coming out of the vents. If it gets real cold, the compressor is very obviously running even though the AC light is off, despite what the technician said. If the air remains warm or is only at ambient, the compressor is indeed off and your car works differently than everyone else's.
I'll try your experiment when the weather gets warmer...right now its 18 degrees in Chicago....so any air coming out the vents will be cold, unless heated.
But I'll say it again, the compressor is powered from the belt system and the compressor's "clutch".....if the clutch isn't engaged the compressor isn't on.....AND on my car the clutch does not engage unless the A/C or front window defroster is turned on.......guess I'm just lucky. (and I'm happy with my 27 mpg city driving on my 3.5 SL.....which is another indication that my compressor with it's associated drag on mpg is not on unless I turn it on.)
As many of you may have found out, when in auto mode, the A/C will be on whether you are cooling or heating the car. The manual states that "A/C off will be displayed" when you hit the A/C button for heat without de-humidification but of course this does not happen. What I have found is the following:
If you want to heat the vehicle without A/C on, set the temperature dial to the desired setting in auto mode and then hit the A/C button twice. The air will continue to heat but no de-humidification will be performed. You can test this behavior by setting the temperature to a level that is well below the vehicle temperature so the A/C is forced on for cooling, then hit the A/C button twice and you'll notice that the air is no longer being cooled. If you then hit the Auto button twice you'll feel the air start to come out cold again.
LMK5, there is no question that this summer the A/C on my 2013 Altima SV 2.5 worked just as you described. When I wanted the A/C off I would hit the A/C button to turn it off. The light would go off, but I could still feel refrigerated air coming through the vents minutes later.
My work-around was to turn climate-control Auto to Off or to turn the climate-control system off completely. The latter turned the fan completely off which was a bummer.
I just went outside to run the test you describe. I am now more confused than ever. I turned the temperature to the lowest setting—60 degrees with Auto On. However, if I hit the A/C button On and Off I can hear the compressor cycling On and Off with the button and feel refrigerated air coming out when On. I would swear this is NOT what was happening last summer. The car has been sitting in a heated garage most of the day with occasional opening and closing of the garage door. The ambient temperature there is 55 but the car interior is much warmer from having driven earlier
Last edited by Drifter_Yank; 01-02-2013 at 06:58 PM.
Perhaps a few cars are experiencing this problem but as you discovered yours works as it should....as does mine. (the compressor ONLY is engaged when the A/C button is pressed and the light on the A/C button is lit)
IF your A/C compressor is contantly running then you may have an issue...but mine does not. In addition, IF your compressor is constantly running you will see a drop in fuel mileage and a loss of performance becaused of the extra drag of an engaged compressor.
IF this is an issue it doesn't seem to be widespread....at least it's not on 3.5 SL's
From the system "OFF" state, I can press the fan increase button - this turns on the fan / system.
If I turn the temperature down low, the AC compressor definitely comes on. The "double-press" of the AC button mentioned in this thread turns the compressor off.
I (sort of) understand the AC coming on in AUTO mode IF I turn the temp low enough to need it. However, it should illuminate the AC light at that point. It also SHOULD NOT turn on the AC if the temp is set high, or if only the fan has been turned on without the AUTO being pressed. If the outside temperature is comfortably low, I should be able to easily enable ambient (unheated or cooled) airflow from the system w/o having to guess whether AC is being used needlessly (and wastefully).
Quote:
Originally Posted by flipn0tic
So this glitch only occurs when using Auto, correct?
It was boggling my mind why I never noticed this issue, but I guess it's because I never use Auto to begin with.
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2013 Altima 3.5SL, Cayenne Red, Beige Leather, BT trunk light mod / footwell light mod, Racing Line FSTB
If it's a widespread problem...I'm shocked, because Nissan has gone out of it's way to claim an industry HIGH MPG on its 2.5 models. So, to design or mis-design a system that sucks MPG out by running a compressor all the time is nuts!
But as I've written before IF my 3.5 SL had the same issue one clue would be my inability to get 27 mpg (mostly city driving) on my 275 hp V-6.
This might be an early production problem, or one that affects the 2.5 engine.
For those that claim that there compressor is always running I'm curious as to your MPG and the performance (ie: pick-up from a stop/power)
Well...my mileage in mostly city driving is better than yours......so I guess your compressor is on.......lucky for me mine isn't having the issue......just screwed up heated seats (as we all have) and the CVT "shudder".
Same issue. I was suspicious that it was running while in "auto" mode while blowing heat. A couple seconds after remote starting the car you can hear the clutch engage for the A/C even when its set to 90 and its 15* outside. You can also feel it kick off if you hit the AC button twice as described.
If it's a widespread problem...I'm shocked, because Nissan has gone out of it's way to claim an industry HIGH MPG on its 2.5 models. So, to design or mis-design a system that sucks MPG out by running a compressor all the time is nuts!
Rob, you are thinking too logically. Having worked for a large OE manufacturer I can assure you bad things DO happen in the design-manufacture cycle as described by LMK5. One thing I will say is it is my experience that if companies waited for the design engineers to be satisfied rather than pushing schedule commitments no new products would ever make it out of the design and testing stage into production.
Back to the specific A/C button topic: At this point I have concluded I will have to wait for warm weather to reevaluate things. However, as previously stated, I am sure my A/C was acting exactly as LMK5 described even though I could not replicate it in my test today. I can assure you I did not drive around with the climate-control system off last summer for no reason.
One thing this points out is that the Owner's Manual is way too general in describing the operation of the climate-control system. Nissan is not unique in this deficiency.
BTW, my calculated mpg has been running slightly higher than rated from the start. However, every tank has been slightly lower than the previous which is starting to concern me. Driving patterns have not changed. Colder, but not cold, weather could explain this. The computer MPG consistently runs 4-5% higher than actual calculations. It has never run less than my calculated MPG. I am sure this is not a coincidence. If you report mileage on the Fed fuel mileage site, they want the calculation inputs not the computer's readout.
Last edited by Drifter_Yank; 01-02-2013 at 11:06 PM.
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