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A/C vent temperature fluctuating?

Tiny
BHAMDOC1973
  • MEMBER
  • 2013 MERCEDES BENZ C250
  • 4 CYL
  • TURBO
  • 2WD
  • AUTOMATIC
  • 64,000 MILES
The driver's side goes from super cold to super hot all of a sudden, after a few minutes of driving then comes back in 20-30 seconds or if you turn off then turn on the car.
Monday, July 11th, 2022 AT 5:01 PM

6 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,702 POSTS
This happens when the rheostat inside the blend door actuator goes bad and is not allowing the controller to be stable. Here is the location of the part so you can check it out. There is no simple test for this, I would try a new part and see what happens. Check out the diagrams (below). Please let us know what you find.
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Tuesday, July 12th, 2022 AT 9:08 AM
Tiny
BHAMDOC1973
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  • 1,581 POSTS
I see. So, what happens if I unplug the left one while the air coming out cold? Will it just stay there?
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Tuesday, July 12th, 2022 AT 9:14 AM
Tiny
KEN L
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Yep, it will stay on the cold setting. Not a bad way to go to get the cold air in this heat.
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Wednesday, July 13th, 2022 AT 11:39 AM
Tiny
BHAMDOC1973
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  • 1,581 POSTS
Does the panel around the carpet need to be removed? I cannot tell from the pictures.
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Wednesday, July 13th, 2022 AT 11:41 AM
Tiny
BHAMDOC1973
  • MEMBER
  • 1,581 POSTS
I unplugged it and went all the way to very hot air.
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Wednesday, July 13th, 2022 AT 12:07 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,702 POSTS
Hmm, it must need voltage to stay in one position, it was worth a try.
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Wednesday, July 13th, 2022 AT 12:38 PM

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