Does the A/C default to ON at every startup?
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2024 E350
Does the A/C default to ON at every startup?
So it's winter time and I've never turned the A/C on during the winter. I have the climate set to AUTO and I noticed that my new E turns the A/C on each time I start the car even if I've previously turned the A/C off.
Someone please tell me there's a way to change a setting so the A/C remembers my last choice (whether ON or OFF). I read the manual and it seems like there's no way to do this with the AUTO setting activated.
If it were summer I would be fine with the A/C turning ON each time, but having to constantly turn it off in the winter would be annoying.
I feel there's no need for A/C in the winter because it uses more fuel and puts more strain on the engine making it slower.
Someone please tell me there's a way to change a setting so the A/C remembers my last choice (whether ON or OFF). I read the manual and it seems like there's no way to do this with the AUTO setting activated.
If it were summer I would be fine with the A/C turning ON each time, but having to constantly turn it off in the winter would be annoying.
I feel there's no need for A/C in the winter because it uses more fuel and puts more strain on the engine making it slower.
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Just because the A/C light is on it doesn't mean that the compressor is actually engaged and running. Think of it as disable/enabled becuse the compressor only runs when it is necessary to provide cooling.
Last edited by ua549; Feb 8, 2025 at 01:34 PM.
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Hope this helps.
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Remember even if it is zero outside, if you put the car in defrost mode, the AC comes on to clear the windshield. In Auto, with the AC on the same: it is on.
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The only time in the winter I leave the AC on is when the windows get fogged.
In Vermont when it is zero, if I hit the defrost and have the AC on, it takes much longer for the heat to defrost the window. With the AC off, I get hot air much quicker.
Turn the AC off in the winter: it will save you money.
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I just read the above thread: Leaving the AC on in the winter decreased the range of the EV by 25/35 miles: It is on and draining the battery. Same thing in an ICE. It is on and will burn more fuel.
The only time in the winter I leave the AC on is when the windows get fogged.
In Vermont when it is zero, if I hit the defrost and have the AC on, it takes much longer for the heat to defrost the window. With the AC off, I get hot air much quicker.
Turn the AC off in the winter: it will save you money.
The only time in the winter I leave the AC on is when the windows get fogged.
In Vermont when it is zero, if I hit the defrost and have the AC on, it takes much longer for the heat to defrost the window. With the AC off, I get hot air much quicker.
Turn the AC off in the winter: it will save you money.
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It’s my understanding that the a/c compressor on the 450 is electrical - not belt driven so it shouldn’t cause any engine strain or use much more fuel other than what it would take for the ISG to replace the energy to the battery.
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I think many are over thinking this. I leave it on auto and the A/C enabled which means the computer manages when the compressor is on based on the real-time conditions. My belief is that any fuel efficiency gained by turning off the A/C manually is negligible at best and may not even amount to any improvement. Not enough to worry about IMO. It's an automatic climate control system. It's likely best to let it determine how to regulate the interior climate and just set the temp.
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Uhm: never thought of that and you may be correct
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I think many are over thinking this. I leave it on auto and the A/C enabled which means the computer manages when the compressor is on based on the real-time conditions. My belief is that any fuel efficiency gained by turning off the A/C manually is negligible at best and may not even amount to any improvement. Not enough to worry about IMO. It's an automatic climate control system. It's likely best to let it determine how to regulate the interior climate and just set the temp.
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Windows down might make sense up to 20/25 mph. I tend to drive a bit faster, often 75 mph +. At that speed, with the windows down, the inside of my car would be like standing out in a hurricane!
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Or open the sunroof in ventilation position but still not ideal. The good thing is as speed increase, the vehicle automatically closes up the sunroof automatically and open up wider when the speed is dropped, this is especially true for ventilation mode.
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I want to add something, especially with all the fires, I recommend using the climate control and let the HEPA filter if EQS and equipped or the activated charcoal cabin air filter in the cabin to do the filtering, instead of, say your lungs.
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W214 E450
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2024 E350
I don't agree with having the AC on during the winter when I'm trying to heat my car. The warm air already lowers the relative humidity in the car. Does anyone run the heat and AC at the same time in your home? I didn't think so.
On my old E class I just set it on Auto with the AC off and I never had an issue with the windows fogging up. Also, it remembered my last setting at each startup, which was the point of my original post.
The car should remember the driver's last setting instead of defaulting to turning the AC on at every startup.
On my old E class I just set it on Auto with the AC off and I never had an issue with the windows fogging up. Also, it remembered my last setting at each startup, which was the point of my original post.
The car should remember the driver's last setting instead of defaulting to turning the AC on at every startup.
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I don't agree with having the AC on during the winter when I'm trying to heat my car. The warm air already lowers the relative humidity in the car. Does anyone run the heat and AC at the same time in your home? I didn't think so.
On my old E class I just set it on Auto with the AC off and I never had an issue with the windows fogging up. Also, it remembered my last setting at each startup, which was the point of my original post.
The car should remember the driver's last setting instead of defaulting to turning the AC on at every startup.
On my old E class I just set it on Auto with the AC off and I never had an issue with the windows fogging up. Also, it remembered my last setting at each startup, which was the point of my original post.
The car should remember the driver's last setting instead of defaulting to turning the AC on at every startup.
The theory is that yes while you were heating the air, it does get warmer but warm air holds more water, even though the humidity is less. That is the relative nature of humidity. That warm, humid air is what now condenses on the cold window and is usually why the fog appears after the heat is turned on..
and yes, there are some interior home units that do exactly this for humidity control and it is called reheat. Effectively you are running a heater with air conditioning or vice versa and it’s about humidity control.
but as all others see, the heating time does take longer during defrost. My preference is AC off until the car heats up. Or I get the car very hot and crack a window for a second to release the moisture out of that air..
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From: Tennessee
W214 E450
I don't agree with having the AC on during the winter when I'm trying to heat my car. The warm air already lowers the relative humidity in the car. Does anyone run the heat and AC at the same time in your home? I didn't think so.
On my old E class I just set it on Auto with the AC off and I never had an issue with the windows fogging up. Also, it remembered my last setting at each startup, which was the point of my original post.
The car should remember the driver's last setting instead of defaulting to turning the AC on at every startup.
On my old E class I just set it on Auto with the AC off and I never had an issue with the windows fogging up. Also, it remembered my last setting at each startup, which was the point of my original post.
The car should remember the driver's last setting instead of defaulting to turning the AC on at every startup.
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2024 E350
If your statement is accurate about the AC compressor not being on all the time if AC is enabled then I would be fine with that.
Can anyone confirm that?
I thought if the AC button is on then the compressor is constantly running.
Can anyone confirm that?
I thought if the AC button is on then the compressor is constantly running.
Last edited by jumpman726; Feb 10, 2025 at 12:29 PM.
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The compressor cycles to maintain the set temperature.
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In the 450 the compressor is all electric (no belt off the engine and so clutchless), variable displacement, and runs off the 48V system rather than the 12V system. It's a variant of the Brose G43852 that has been used in the S class since 2021. In the 350, though, it's a Denso 6SAS14C, belt driven with a clutch, but still variable displacement.
Variable displacement compressors are much more efficient because they can scale up/down their cooling output to meet the needs of the climate control system. If it's not needed it will be at minimum displacement and have basically no effect and draw an insignificant amount of power, or on the E350 it will disengage the clutch and draw no power at all.
I didn't realize until researching this that the E450 gets a slicker compressor than the E350, and to my mind it's another reason to get the E450 -- the AC should keep blowing cold even if the engine stops as part of the auto stop/start.
Variable displacement compressors are much more efficient because they can scale up/down their cooling output to meet the needs of the climate control system. If it's not needed it will be at minimum displacement and have basically no effect and draw an insignificant amount of power, or on the E350 it will disengage the clutch and draw no power at all.
I didn't realize until researching this that the E450 gets a slicker compressor than the E350, and to my mind it's another reason to get the E450 -- the AC should keep blowing cold even if the engine stops as part of the auto stop/start.
Last edited by gleam; Feb 10, 2025 at 03:57 PM. Reason: remove E53 since it uses a slightly different model
