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Rear Air Con Blowing Hot

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Old Apr 28, 2023 | 03:34 AM
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W212 E500
Rear Air Con Blowing Hot

G'day,
I have a 2010 E500/550 that is blowing hot air from the rear vents, it is a 3 zone system. I have read somewhere where a controller/component may be at fault, but I am blowed if I can find the post again now I have time to have a look. Have done various searches and gone through multiple pages but no luck so far. Can any one point me in the right direction?
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Old Apr 28, 2023 | 04:26 AM
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W212 MY'14 M276-3.5NA @75kMi
blend door control module

the question is where is the rear blend door module in the main HVAC Box inside the dasboard or in the back side of the central console?

Scan the AAC module to confirm active faults ...
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Old Apr 28, 2023 | 05:31 AM
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'71 Pinto
Provide VIN.
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Old Apr 28, 2023 | 06:15 AM
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W212 E500
WDD2120722A027908

Thanks
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Old Apr 28, 2023 | 06:39 AM
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'71 Pinto
Could be temperature sensor, actuator motor, or rear operating unit best to have someone pull codes using Xentry (MB diagnostics) before replacing part(s).






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WDD2120722A027908.pdf (609.3 KB, 189 views)
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Old Apr 28, 2023 | 02:45 PM
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front or back ??

This exemplify how many parts can cause the rear A/C issue you are experiencing.

You may want to listen or feel for the central console fan blowing air = good!
This is an easier problem with an easier fix than dealing with the main dashboard unit.

Let the scanner guide your reality with clues.
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Old Apr 28, 2023 | 06:44 PM
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W212 E500
Thanks for replies. front is fine and A/C system was recently serviced with no other issues. My scanner, which I do not have huge amount of confidence in how deep it goes, did show a issue with front footwell thermistor being "faulty", which was the old broken wire when replacing the cabin filter trick which has now been repaired. There are no other AAC errors being picked up. The rear fan blows hard and speed can be controlled by the up /down buttons, just warm though. As per konigstiger I will get a "proper" scan done and see if that points towards the blend actuator, although as mentioned I am sure I read somewhere on the inter webs of a controller/component being a known culprit. Will update outcome.
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Old Apr 28, 2023 | 07:11 PM
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W212 MY'14 M276-3.5NA @75kMi
blend door collection 😳

Originally Posted by Helebah
Thanks for replies. front is fine and A/C system was recently serviced with no other issues. My scanner, which I do not have huge amount of confidence in how deep it goes, did show a issue with front footwell thermistor being "faulty", which was the old broken wire when replacing the cabin filter trick which has now been repaired. There are no other AAC errors being picked up. The rear fan blows hard and speed can be controlled by the up /down buttons, just warm though. As per konigstiger I will get a "proper" scan done and see if that points towards the blend actuator, although as mentioned I am sure I read somewhere on the inter webs of a controller/component being a known culprit. Will update outcome.
You're on the right track!

Rear fan blows good
Broken footwell sensor replaced
A/C serviced.

The blend door actuators are built with unsoldered electronics for limited reliability. Here it does look like they require additional service. There are 6 of 'em all identical...

FYI: you may have a bad actuator combined with zero fault
✌️
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Old Apr 28, 2023 | 10:30 PM
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2014 - W212.065 - E400 ( M276.820, 3 liter Turbo) RWD not Hybrid
Dig deeper.................





Have fun....................


I have 580 , so no rear blend door. Xentry can activate this door/actuator to test.
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Old Apr 29, 2023 | 07:18 PM
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W212 E500
Thanks S-Prihadi, that information is great and will give me enough info to probably dig a big hole for myself... and I am sure others will use it as well
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