Question about Climate Control not maintaining temp correctly
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Question about Climate Control not maintaining temp correctly
2011 e350 4matic
recently, I had the hvac head unit replaced by the dealer because the AC light was stuck on. Tech said the head unit controller had to be replaced. Other than the unit being "stuck" in AC mode, no issues regulating temperature.
Got the car back, and on a 55 degree day with the temp set to 70 in auto it just kept feeling hotter and hotter. The only way I could get cool air was to lower the system to LO or MAX COOL.
Took it back to the dealer and it was a 70 degree day, so of course the system did not duplicate the condition and ran AC, regulating temp properly. I had them check that the dampers were synced as part of installing the new head unit and they assured me they were and that it was installed per the SOP.
When I got the car back the very next day (which was cooler) it did the same thing.
If I leave the CC set to 61 or 62, it "kind of" works, regulating a temp I would say is probably more like 72 or so. It hasn't been warm enough outside to know if this will "go away" when the system clearly needs to call for AC because it is warmer outside than in but it is frustrating on those in between days. It is clearly not working the way it is supposed to.
Good news is under manual overriding I can get the use of AC or heat depending on what is needed. But it is not operating as designed and I leave my car in auto constantly - set it and forget it unless I need defrost.
I saw posts about trying a reset or using Easter egg but was hoping someone would have some insight before I try to get the dealer to attempt to fix this again. They were no help last time.
recently, I had the hvac head unit replaced by the dealer because the AC light was stuck on. Tech said the head unit controller had to be replaced. Other than the unit being "stuck" in AC mode, no issues regulating temperature.
Got the car back, and on a 55 degree day with the temp set to 70 in auto it just kept feeling hotter and hotter. The only way I could get cool air was to lower the system to LO or MAX COOL.
Took it back to the dealer and it was a 70 degree day, so of course the system did not duplicate the condition and ran AC, regulating temp properly. I had them check that the dampers were synced as part of installing the new head unit and they assured me they were and that it was installed per the SOP.
When I got the car back the very next day (which was cooler) it did the same thing.
If I leave the CC set to 61 or 62, it "kind of" works, regulating a temp I would say is probably more like 72 or so. It hasn't been warm enough outside to know if this will "go away" when the system clearly needs to call for AC because it is warmer outside than in but it is frustrating on those in between days. It is clearly not working the way it is supposed to.
Good news is under manual overriding I can get the use of AC or heat depending on what is needed. But it is not operating as designed and I leave my car in auto constantly - set it and forget it unless I need defrost.
I saw posts about trying a reset or using Easter egg but was hoping someone would have some insight before I try to get the dealer to attempt to fix this again. They were no help last time.
Last edited by frostsdad; Apr 11, 2015 at 07:00 PM. Reason: Added model and year
MBWorld Fanatic!
Joined: Nov 2009
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From: Southeastern USA
2010 E350 Luxury Sedan, Engine 272 (V6)
SCAN?
Interesting. I have the same or similar problem and have asked the question, but no responses. In winter and summer, Auto works just fine set on 72 degrees. Only a problem when outside temps are cool in AM and warm in PM. Lowering to Hi Cool for about 5+ minutes seems to reset it to normal - until start car again.
Is there a scan for the HVAC system that might show what the problem is? I would take it to an indy for the scan. M-B dealer is too far away and far too costly for this.
Is there a scan for the HVAC system that might show what the problem is? I would take it to an indy for the scan. M-B dealer is too far away and far too costly for this.
Out Of Control!!
Joined: Apr 2019
Posts: 11,924
Likes: 6,776
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
TEMP HOT/COLD
Interesting. I have the same or similar problem and have asked the question, but no responses. In winter and summer, Auto works just fine set on 72 degrees. Only a problem when outside temps are cool in AM and warm in PM. Lowering to Hi Cool for about 5+ minutes seems to reset it to normal - until start car again.
Is there a scan for the HVAC system that might show what the problem is? I would take it to an indy for the scan. M-B dealer is too far away and far too costly for this.
Is there a scan for the HVAC system that might show what the problem is? I would take it to an indy for the scan. M-B dealer is too far away and far too costly for this.
You can begin by replacing your $10 cabin filter. Air con needs good air flow.
MBWorld Fanatic!
Joined: Nov 2009
Posts: 2,616
Likes: 160
From: Southeastern USA
2010 E350 Luxury Sedan, Engine 272 (V6)
Ironically I can change the cabin filter in every car I have ever owned that had one - except M-B E350. Currently a Toyota Tacoma and Nissan Rogue.
Not into removing panels, etc. Too much bending, etc. and too much opportunity to break a tab or something.
Cabin filter replaced 8,000 miles ago. Car is garaged 90% of time. Will probably get indy to replace it next time serviced.
Thanks for your advice .
Out Of Control!!
Joined: Apr 2019
Posts: 11,924
Likes: 6,776
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
Thanks. I'll get the indy to scan it next time I take it in. My DIY days are pretty much behind me so do not have a scanner.
Ironically I can change the cabin filter in every car I have ever owned that had one - except M-B E350. Currently a Toyota Tacoma and Nissan Rogue.
Not into removing panels, etc. Too much bending, etc. and too much opportunity to break a tab or something.
Cabin filter replaced 8,000 miles ago. Car is garaged 90% of time. Will probably get indy to replace it next time serviced.
Thanks for your advice .
Ironically I can change the cabin filter in every car I have ever owned that had one - except M-B E350. Currently a Toyota Tacoma and Nissan Rogue.
Not into removing panels, etc. Too much bending, etc. and too much opportunity to break a tab or something.
Cabin filter replaced 8,000 miles ago. Car is garaged 90% of time. Will probably get indy to replace it next time serviced.
Thanks for your advice .
AAC uses a dozen sensors. Nothing is directly obvious unless there's an active fault available.
A lot of times the tiny harness to the footwell temp sensor ends up ripped apart during cabin filter service (does report as a fault).
8kMi filter is perfectly fine without replacing.
Raise your fan speed to help circulate more cabin air throughout.
FYI: AirCon is never great due to the nearby 200°F heater core kept fully heated without any control. This helps dry A/C system to stop smelly bacterial/mildew growth.
