GibbsKnot

Hello fellow C300 owners -

I just purchased my 2022 C300 about a month ago here is the US & I wanted to see if others are getting the following behavior with theirs:

Whenever the engine is off due to the auto start/stop system, the air from the AC vents gets warm. As soon as the engine kicks back on, the air cools back down again. I also notice that the engine restarts after maybe just a minute or so. It doesn’t seem like it can remain off for very long. This is very different from my 2021 GLE 53 where even after the engine is off for several minutes at a red light for example, the air remains nice and cold.

I am curious if this is normal in the C300 and if so, does anyone know what is behind the difference in behavior? I could be wrong, but my understanding is that in both the C300 and the GLE 53, the AC compressors are electrically driven.

Thanks in advance!

luciferclefcapr

Hi! I have a C200 in The Netherlands here and I have the same experience. Whenever the engine shuts off (auto start / stop) for example at a traffic light, the air starts to get warmer. I think this is logical if the airco compressor is being driven by the engine. It's to bad but not much we can do about this I suppose :|.

Dstopsie

I have the same issue on my 2022 C300 and my 2020 C300 did the same thing. Air got warmer when I had the auto start engaged.

Heloflyer68

Not 100 percent sure, but in other German cars that I have driven before the 300 in the US had similar behavior. The draw of electricity to run an AC compressor is way to high for a battery installed on a medium size sedan like the C class. I know for a fact that the car will stay with the engine OFF when either:
- the voltage of the battery falls below a certain amount
- or the temperature sensed inside the cabin falls below a temperature spread from the user setting.
Difference in temperatures perceived by the user in the cabin changes by size of the air conditioner installed on each vehicle when the motor is not running. (A larger SUV will have larger radiators though the air flow will stay cooler for longer time)
Electric vehicles run air conditioning units because the size of the batteries installed are nothing like the one we have in the C class.
I do not base my statements based on technical knowledge of this particular vehicle but on previous owned ones and other systems I’m familiar with.

alexasa

iTrader: (1)

pretty sure the air is just recirculated by the fan during the auto off period.

Serg675

I haven't noticed that went air is warmer during auto stop but haven't payed attention to it. Will see. I guess it depends on the size and charge level of the 48 volt battery system so smaller cars will not benefit much from auto stop due to smaller battery size.

js_cls

The C-Class features a slightly different MHEV system than the 450, 53, and 580 cars such as the E, CLS, S, GLE/GLS. Unlike those cars, the AC in the C-Class is still belt driven rather than by the 48v system.

GibbsKnot

Interesting! That would totally explain it.

818benz

After reading this last night, I looked out for it all day while driving today. The A/C on LOW did not get warmer when the engine was on auto off. Maybe to prevent this, the engine turned on twice after a min at a red light, though it was almost 95 in the valley today. It doesn't turn on at a red light often but definitely didn't get cooler today.

Once, I noticed the airflow wasn't cold enough after setting it on LOW with max fan. Just restarted the engine and made it work normal. Only happened once though.

Dstopsie

hi 818benz

I live in the valley too here in Los Angeles. I do notice the AC isn’t as cold when I have the start stop engaged and does get colder when I turn it off. It did this on my 2020 C300 too.

Serg675

From my observation I don't see that temprature of the air coming from the vents is warmer during auto stop. But than hotter the temperature outside than less time engine stays off. Engine is not turning off during stops at all even when cabin is not cooled down yet. And if I drive during late evening with all windows down, sun roof opened and climate off then engine stays off during stop as long as stop itself. Not sure if AC compressor is driven by belt but I see one belt under the hood.