Climate control question
Thread Starter
Senior Member
Joined: Aug 2005
Posts: 406
Likes: 103
Climate control question
Hello. In my w221 I always had the comate control at 70 in auto. Fan speed was somewhat predictable and queit. It would warm up the cabin on slow speed and keep it warm quitely. In hot weather in would do the same.
In my 222, the fan action is noisier. Also I notice the fan speed flactuates when I stop at a red light or if I slow down. It feels like the fan speed often goes up and down way too often. I tried all 3 settings, Diffuse, medium and focused.
I am wondering if this is normal, because in my w221 the climate control was hardly notoicable while doing its thing. IN this car Im constantly going from 68 and 70 to calm the stem down so its not too noisy. Often times I lower the fan speed to 2 or 1 just to not hear it.
Thank you in advance.
In my 222, the fan action is noisier. Also I notice the fan speed flactuates when I stop at a red light or if I slow down. It feels like the fan speed often goes up and down way too often. I tried all 3 settings, Diffuse, medium and focused.
I am wondering if this is normal, because in my w221 the climate control was hardly notoicable while doing its thing. IN this car Im constantly going from 68 and 70 to calm the stem down so its not too noisy. Often times I lower the fan speed to 2 or 1 just to not hear it.
Thank you in advance.
Out Of Control!!
Joined: Apr 2019
Posts: 11,964
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
Forcing the cabin blower to speed 1 disables cooling efficiency 
Aircon needs AIR FLOW through the heat exchangers, either the A/C evaporator or heater core.
Try replacing a new cabin filter to help the air flow.
Aircon needs AIR FLOW through the heat exchangers, either the A/C evaporator or heater core.
Try replacing a new cabin filter to help the air flow.
Last edited by CaliBenzDriver; Mar 30, 2026 at 07:57 PM.
Super Member
Joined: Jun 2025
Posts: 784
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From: USA
Your W222 is overreacting because the auxiliary water pump is likely weak or dead. That pump keeps hot coolant flowing through the heater core at idle. When it fails, the system thinks it’s losing heat and cranks the fan to compensate hence the surging at red lights. Check that first.
Thread Starter
Senior Member
Joined: Aug 2005
Posts: 406
Likes: 103
Your W222 is overreacting because the auxiliary water pump is likely weak or dead. That pump keeps hot coolant flowing through the heater core at idle. When it fails, the system thinks it’s losing heat and cranks the fan to compensate hence the surging at red lights. Check that first.
Thank you. Would this happen even in warmer days with ac on ? Heat worked fine. I was thinking maybe fan regulator ? But then the fan would not work or be stuck on high.
I replaced aux heater pump on my w221 last September. It was not a fun job.
Last edited by tbilisi79; Apr 1, 2026 at 06:59 AM.
