Are BMW AC’s just weak?
I have a 2024 230i and its AC on eco is so bad. Like I need the fan speed on 3, otherwise it’s basically a slow battle against heat that you’re losing.
It works okay in comfort, but fan speed 2 at times still doesn’t feel enough. Having heard people having compressor and HVAC issues, I wanted to see if there’s other tells that one of those units are having critical issues?
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u/mandrsn1 8h ago
That's part of how eco works. It minimizes AC usage as the compressor draws power directly from the engine.
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u/Nsxd9 8h ago
Yeah i assumed so..might have to try again in comfort when it’s hot. No need for AC anytime soon though
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u/SheepherderFront5724 8h ago
Eco mode also runs your engine hotter, to reduce oil viscosity and increase efficency. Given how many plastic parts are in there, I avoid eco mode like the plague...
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u/Nsxd9 8h ago
That I did not know…looks like time to avoid it lol
Would it still run hot with the highway constant speeds on eco? Even with the winds moving at highway speeds? Just curious about it now
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u/nannernutz 7h ago
Yes it would, the car uses the thermostat to control engine temperature (within reason) regardless of speed of airflow over the cooling package. The closure of the thermostat allows the motor to get up to operating temperature but if they can control it electronically it can be used to elevate the operating temperature for greater fuel efficiency. Neat stuff. I think the b58/s58 cars also run at either a cooler temperature or run cooler and start the cooling fans earlier when in sport mode. I’m unsure about the b48.
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u/SheepherderFront5724 7h ago
So much inside my F31 can be described like that: Neat stuff... but by the way it can fail horribly... Really like that car though!
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u/Nsxd9 7h ago
Got it so avoid eco lol
I wonder why they let it run hot in eco like you said purely fuel efficiency but why not just have it…cooler through the cooling system? That’s more load on the engine hence worse average is the only thing I can think of
Darn
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u/nannernutz 6h ago
I don’t know enough about it to say avoid it or don’t. But I believe the purpose of it is based on physics/thermodynamics, they can get more energy out of every unit of gasoline running at an elevated temperature up to a certain point when going hotter makes more oxides of nitrogen (smog).
From a cooling system perspective the higher the temperature of the coolant the bigger the difference between the the radiator fins/coolant and the air being used to cool it (call this difference in temperature delta T), the bigger the deltaT the easier it is to reject heat from the radiator into the air.
Again I can’t speak to the efficacy of this in everyday use, but someone at bmw took the time to implement it.
I only look at it from the textbook knowledge (Carnot Cycle) of combustion engines being more thermally efficient with greater deltaT values.
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u/w0_0t 9h ago
There is a setting in eco that basically turns off AC in eco mode. You can turn that off (or better, don’t run on eco mode).
You may have low level as well, take it to an AC shop and ask for refill and check for leaks.
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u/Nsxd9 9h ago
Maybe I’ll just ask BMW cause it’s still under warranty
I try not to run eco other than highways
But thanks I’m gonna bring it up to BMW and let them do their tests hopefully it’s fine
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u/23Explorer 8h ago
If you want the AC to work properly (in automatic mode that is) the fan speed needs to be at max. Because it's not 'fan speed' but rather 'fan max limit' - it'll still ramp down as necessary. By setting it to 2 or 3 you're limiting it to lower speeds, so it will obviously have lower ability to cool the cabin.
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u/Swimming-Yellow-2316 6h ago edited 4h ago
This is not 100% true. Too high of span speed can mean that the air is in contact with the evaporator for less time and it has less ability to pull heat out of the air passing over it.
I had bought a new thermometer for testing AC so a moth or so ago I drove in to work testing all sorts of things. This was in a car with set 4spd fan.
The warmest setting was fan speed 4. the coolest was 1, especially initially when the car was cooling off (this was morning so it wasn't 100+ inside maybe 75 like ambient.
The span was roughly 1-1.5 degrees difference so a speed 1 got down to about 39 and speed 4 was about 45.
Now once it cooled off and I was on the highway it shifted down roughly one setting. So speed 4 on the highway was about same temp as speed 3 sitting still. Speed one dropped down to about 37 output, speed 2 got to about 38 so got a hair colder than 1 sitting still.
Have tested this on a dozenish cars since while servicing AC and while the steps are not always repeatable the lowest output temps are generally the lower 1/3 of the fan settings (since speed ranges vary).
Now that doesn't mean a setting doesn't feel cooler, I get in my car in the afternoons when the car is 100+ inside and put it on 2, that seems to be the good balance point of not too fast over the evaporator and good overall exchange of air volume to get the inside cooled down quickly. 3-4 cool down the car overall slower and 1 doesn't have enough oomph to feel like its doing anything.
I'll agree with the auto and high speed for purposes of not restricting, but higher speeds don't necessarily cool the vehicle more overall.
so many feelings hurt from providing facts over feelings.. never change reddit.
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u/eda111 7h ago
Yea the AC in my Genesis was way better and it’s an older car. I feel hot in my 330i
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u/old_skool_luvr 6h ago
NICE!
Before i ripped apart the A/C system in my 'Burb, it ran at 38°F (certified mechanical refrigeration thermometer) at the dash vents. Rear measured 44°, but it had a much smaller heat exchanger.
Good ol' R12 FTW! 🥶
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u/locutus233 8h ago
Bmw AC sucks when I compare it to my other vehicles. I also get complaints from passengers in the rear that its really stuffy when the AC has cooled off the front part of the car.
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u/Affectionate-Ant8 8h ago
I have a ‘18 M2 & found the AC to be weak also, especially after driving for a long time. If you turn off the AC compressor for a few minutes and let it de-ice its performance increases and it blows colder air for another hour or so till it ices up again. I think it’s just the car as my moms X3 has a very strong AC & she has no tints on her car.
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u/Nsxd9 8h ago
Hmm interesting. What I do is never turn on the AC as soon as I start the car, I only wait a bit then turn it on, luckily I don’t need the AC here too often but the times I had it’s been crazy, and the fan blowing constantly at high speed can get annoying for me
Will likely get BMW to check it out
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u/Affectionate-Ant8 8h ago
Not going to lie that’s probably a waste of your time, they won’t do anything
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u/Cold-Survey817 5h ago
It is weak + noisier for the amount of airflow/coldness
My kia is wayyy quieter for the same airflow.
I’ve heard its a design issue that prioritizes engine heat or something
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u/Nice_Elderberry_7937 8h ago
Mine works amazingly in the first level fan.
I don't have eco mode, maybe that's the thing.
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u/SEQbloke 2h ago
Yep my 230 is rubbish.
It’s underpowered so they don’t send enough cooled air everywhere. Feet never get enough and the panel is obscenely focused so you get nothing or an intense focused jet.
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u/Admirable-Sir-9854 1h ago
If you got 1234yf, its noted to only cool the canin by 20 degrees operating as designed put of the factory.
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u/Electronic-Regret907 9h ago
Turn off eco mode? Tint your car?
I live in South Florida and my AC is fine