A/C blower issue?

2008 MERCEDES BENZ S550
181,000 MILES • V8 • 4WD • AUTOMATIC
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BHAMDOC1973
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The temperature of the air coming out of vents is always super cold, so no issues there. Blower speed changes on its own. I can drive and it goes from say a 1 with very little air coming out to 7 which is max on otw own. Stays for about 30 seconds then toes back to 1. While it's on 7 i can adjust the speed to 6 or 5 or whatever i need. Trying to see if this is a blower or a resistor issue.
Jul 25, 2022 at 8:18 PM
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SQM
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Hello,

Does this only happen when it is in Auto mode?
If so, the issue is the inside temperature sensor. It is not able to report proper temperature and the fan is just trying to achieve the set temperature by going from low to high.
This is part of the HVAC module.

I had the same issue with my CLK and just ended up using the manual mode to bypass the issue.

Let me know of any questions.
Thank you.
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Jul 25, 2022 at 10:06 PM
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BHAMDOC1973
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It does that not when it's in Auto mode. I thought about it, but when you do it in automate I don't think it will do it but I also don't think it would cool. I never understand Auto-mode fully, so does this mode control the speed of the blower as well as the temperature of the air coming out? or just temperature. I will try again and see.
Jul 26, 2022 at 7:28 AM
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BHAMDOC1973
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Tried auto option and same thing. Just randomly goes from high to cough a bit then down to 1 or none.
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Jul 26, 2022 at 8:21 AM
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BHAMDOC1973
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This.
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Jul 27, 2022 at 1:12 PM
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SQM
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Were you able to fix the wire? It really looked like the issue is that wire.
Jul 28, 2022 at 8:56 PM
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BHAMDOC1973
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I ordered another one. These are not serviceable.
Jul 29, 2022 at 12:44 AM
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SQM
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Let me know how it turns out.
Jul 29, 2022 at 4:13 PM
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BHAMDOC1973
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It was the motor assembly. thank you
Jul 29, 2022 at 5:22 PM
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SQM
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Glad you got it figured out!
Jul 29, 2022 at 8:19 PM