heat / ac issue
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From: NYC
'12 CLS 550 4matic
heat / ac issue
I notice it in all of my Benzes, loaners, etc. When I push the auto temp button, the light for the a/c comes on. I can understand if the exterior temp is higher that what I chose, but in the winter it's a pain in the *** to always have to shut it off!
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From: Placitas, NM
E550
And, I might add, it's good for the AC compressor to be run regularly, rather that shut down all winter/spring/fall.
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From: Placitas, NM
E550
I might also add, AC compressors used to be a high maintenance item. Not any more. I haven't had a compressor go out, or had to top off refrigerant, in over 35 years. (Now, in the 60's and 70's, it was a different story. Of course, the cars weren't worth a crap, either!)
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From: Southeastern USA
2010 E350 Luxury Sedan, Engine 272 (V6)
Not sure you can turn the AC off even when you press the AC button and the light goes out.
I turn my system off, then use fan button to start the fan and then press AC button to turn off the compressor and have just the ventilation open. Can still use fan button and AC light stays off. That's the theory.
BUT, I'm not sure that really works. If temp is high outside, cold air comes out of the vents or warm air if cold outside. So, is compressor always on if fan or mode is turned on?
In my previous car with Auto HVAC, you could turn it off, then hit AC button for on and then hit it again for off. Compressor would remain off, but you could use fan to bring outside air in.
I turn my system off, then use fan button to start the fan and then press AC button to turn off the compressor and have just the ventilation open. Can still use fan button and AC light stays off. That's the theory.
BUT, I'm not sure that really works. If temp is high outside, cold air comes out of the vents or warm air if cold outside. So, is compressor always on if fan or mode is turned on?
In my previous car with Auto HVAC, you could turn it off, then hit AC button for on and then hit it again for off. Compressor would remain off, but you could use fan to bring outside air in.
Last edited by El Cid; Jan 31, 2012 at 11:00 AM.
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Porsche Macan S SportDesign / Ex M-B's: 11 & 10 & 06 E350's, 02 S500
Do you guys have the A/C on when you use the Heater? I always thought this would be bad, as I equate A/C with cold air only?
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From: Sarasota FL
2020 E450 Wagon
In these days where fuel economy takes up so much of automotive engineers time, spinning the A/C compressor under all most all conditions is beyond my comprehension. I have the same struggle with my 2012 Jeep G. Cherokee. You really have to work at it to shut off the A/C compressor. Trust me when I tell you that A/C repairs, including compressor replacement, is still a good share of our business. Yes, operating the compressor will dehumidify the interior air. But when the relative humidity approaches 50% or less, it is not really necessary when all you really want is a little heat on your toes.
A/C compressors are much more efficient than they once were. But they still cost a couple MPG. Hey, make sense to me, run the compressor all the time and shut the engine off at stop lights
A/C compressors are much more efficient than they once were. But they still cost a couple MPG. Hey, make sense to me, run the compressor all the time and shut the engine off at stop lights
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From: Earth
Porsche Macan S SportDesign / Ex M-B's: 11 & 10 & 06 E350's, 02 S500
Forgot about the MPG factor. Makes it pointless for me to even consider running the A/C on when the heater is on, especially considering I live in a mostly dry climate.
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From: Southeastern USA
2010 E350 Luxury Sedan, Engine 272 (V6)
I believe that in most every car manufactured today, the AC comes on whether set to heat or cold. In fact, if you turn on the Defroster, it turns on the AC to remove moisture from the air.
As for turning off AC compressor, only way is to use OFF button, but then you get no airflow from the vents.
See my comment above.
As for turning off AC compressor, only way is to use OFF button, but then you get no airflow from the vents.
See my comment above.
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From: Saskatchewan
1969 280S, 1991 300E
It makes little sense to my why anyone would be worried about 1-2MPG difference while running the AC compressor when you're talking about a $70,000 vehicle.
Is it that you're concerned about the environmental impact or the extra 40 miles you'll get out of your tank, which will save you $5?
Am i in the minority on this one?
Is it that you're concerned about the environmental impact or the extra 40 miles you'll get out of your tank, which will save you $5?
Am i in the minority on this one?
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Porsche Macan S SportDesign / Ex M-B's: 11 & 10 & 06 E350's, 02 S500
If it's necessary and takes away 1-2 MPG then that's fine, but if it isn't necessary, then I'll take 1-2 MPG without question.
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From: NYC
'12 CLS 550 4matic
A lot of interseting points above! Personally, I could care less about the MPG, I write off the gas anyway. To me it's the annoyance of having to always shut the button and the fact that it comes on in the first place. I don't notice it in the Porsches I own or any prior owned BMWs. Although my last BMW was a new 04'. I only notice it in Benzes.
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From: North Carolina
2010 E350, 2015 S550
It makes little sense to my why anyone would be worried about 1-2MPG difference while running the AC compressor when you're talking about a $70,000 vehicle.
Is it that you're concerned about the environmental impact or the extra 40 miles you'll get out of your tank, which will save you $5?
Am i in the minority on this one?
Is it that you're concerned about the environmental impact or the extra 40 miles you'll get out of your tank, which will save you $5?
Am i in the minority on this one?
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Joined: Feb 2009
Posts: 280
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From: Sarasota FL
2020 E450 Wagon
Blue Efficency?
The wear & tear and mileage issues are just side bars to the main point of this thread-that the climate control system appears to be programed to run the A/C compressor at times when it is clearly not needed and, at least for some of us, not desirable.
I have been servicing Mercedes automatic climate control systems since the 1970's and have learned that extracting the desired result from each version (maybe 6-8 variations) requires a little trial and error. It used to be that if the compressor off or economy button was pushed the compressor was OFF! We have been a 212 owner for only a few weeks, so I haven't had much time to play with it. But at mild temperatures the climate control unit at times unnecessarily defaults to compressor operation.
I have been servicing Mercedes automatic climate control systems since the 1970's and have learned that extracting the desired result from each version (maybe 6-8 variations) requires a little trial and error. It used to be that if the compressor off or economy button was pushed the compressor was OFF! We have been a 212 owner for only a few weeks, so I haven't had much time to play with it. But at mild temperatures the climate control unit at times unnecessarily defaults to compressor operation.
Last edited by GermanCars; Jan 31, 2012 at 11:18 PM.
Super Member
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From: Saskatchewan
1969 280S, 1991 300E
I highlighted it for you. If you re-read my post, i was asking about whether it's an environmental issue, or monetary...The money thing wasn't an issue until i mentioned it, but it's typically a factor when you're speaking about fuel mileage.
In these days where fuel economy takes up so much of automotive engineers time, spinning the A/C compressor under all most all conditions is beyond my comprehension. I have the same struggle with my 2012 Jeep G. Cherokee. You really have to work at it to shut off the A/C compressor. Trust me when I tell you that A/C repairs, including compressor replacement, is still a good share of our business. Yes, operating the compressor will dehumidify the interior air. But when the relative humidity approaches 50% or less, it is not really necessary when all you really want is a little heat on your toes.
A/C compressors are much more efficient than they once were. But they still cost a couple MPG. Hey, make sense to me, run the compressor all the time and shut the engine off at stop lights
A/C compressors are much more efficient than they once were. But they still cost a couple MPG. Hey, make sense to me, run the compressor all the time and shut the engine off at stop lights
A lot of interseting points above! Personally, I could care less about the MPG, I write off the gas anyway. To me it's the annoyance of having to always shut the button and the fact that it comes on in the first place. I don't notice it in the Porsches I own or any prior owned BMWs. Although my last BMW was a new 04'. I only notice it in Benzes.
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From: Central Pennsylvania
2012 S350 Bluetec 4Matic, Diamond White, P2
The compressor itself does not run all the time. It has a clutch and is electronically activated. Even though the light for the A/C may be on, this only means that the system that controls it is on. If the outside temperature is cold and you are running the heat, the compressor is not used often if at all. For full defrost/defog, the compressor is on because of the additional drying benefits of ac systems (mentioned above somewhere). The default setting is probably ideal for 99% of the folks that buy this car. It is good that MB gave us the option to prevent the compressor from coming on for us 1 percent-ers that wish to completely disable it at times. I have run my Bluetec with it on and with it off and can tell you that there was not a measurable difference in fuel economy, with some of my highest mileage tanks occurring with the A/C light on. Of course, the massive torque of the Bluetec spins the accessories effortlessly and does not take the hit a gas engine may.
Last edited by ImInPA; Feb 1, 2012 at 04:44 PM.
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Porsche Macan S SportDesign / Ex M-B's: 11 & 10 & 06 E350's, 02 S500
You know what, I gotta agree with PA on the MPG thing, now that I really think about it.
In any of my modern cars, namely my E's, I've never noticed a measurable drop in MPG with the A/C on. I still have the theory of it embedded in my head, though. I actually remember some of my best MPG coming while my A/C actually happened to be on, I think.
In any of my modern cars, namely my E's, I've never noticed a measurable drop in MPG with the A/C on. I still have the theory of it embedded in my head, though. I actually remember some of my best MPG coming while my A/C actually happened to be on, I think.
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From: Southeastern USA
2010 E350 Luxury Sedan, Engine 272 (V6)
CR Test
You know what, I gotta agree with PA on the MPG thing, now that I really think about it.
In any of my modern cars, namely my E's, I've never noticed a measurable drop in MPG with the A/C on. I still have the theory of it embedded in my head, though. I actually remember some of my best MPG coming while my A/C actually happened to be on, I think.
In any of my modern cars, namely my E's, I've never noticed a measurable drop in MPG with the A/C on. I still have the theory of it embedded in my head, though. I actually remember some of my best MPG coming while my A/C actually happened to be on, I think.
Cars are aerodynamically designed for least wind resistance with windows up.
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From: Sarasota FL
2020 E450 Wagon
We are not always driving at high speed with the windows up. What about enjoying some rare moderate temperatures (high 60's-low 70's) with the windows and/or sunroof open at moderate speeds. Why can't we have a little fresh air without the compressor operating? I'm sure there is a way, just haven't had the time to figure it out as I'm only in the car occasionally. Right now it is definitely SL weather so the sedan is getting light duty 
And.............the SL has an A/C off button
And.............the SL has an A/C off button
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Joined: Nov 2009
Posts: 2,616
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From: Southeastern USA
2010 E350 Luxury Sedan, Engine 272 (V6)
Maybe
However, in my Benz, even if I turn AC off with the AC button, cold air comes out if temp is about 7-10 degrees higher than the temp setting on the dispaly panel. Does the same thing with heat if temp is 7-10 degrees lower than setting on panel.
So, does the temp setting actually cause the compressor to come on? Or the heat or AC?
BTW, the AC light does not come on when it does this, but air coming out of vents is definitely cold (or warm) air.
I enjoy riding with the sunroof open and maybe a window open when temps are nice.
