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Marty
Marty, Mercedes Technician
Category: Mercedes
Satisfied Customers: 53151
Experience:  Bosch Certified Master Tech. Over 35 years experience.
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Marty, I have a Mercedes Benz 420 SEL with vin

Customer Question

Hi Marty, I have a Mercedes Benz 420 SEL with vin WDB1260352A518382. The problem i have to turn the heating scroll wheel to max to get any heat from the vents. I have already replaced the switch panel, the mono valve and the kilma relay but the problem persists. What could be the cause. I tried looking for the electronic swithing unit but could not find it. Ive been wracking my brain trying to figure this out, any help would be much appreciated. Regards
Submitted: 1 year ago.
Category: Mercedes
Expert:  Marty replied 1 year ago.

Hi, the in car temperature sensor can cause this problem. Check the sensor and see if it is disconnected and see if the suction hose to the sensor is connected. I suspect that you will either find the hose or wiring disconnected or a faulty sensor.

Customer: replied 1 year ago.

Hello Marty, thank you for the responce, is the part number A0008306108?

Expert:  Marty replied 1 year ago.

That's the part number for the blower for the sensor. I've only replaced 1 or 2 over the years but you should check to be sure there is suction at the in car sensor. The sensor is located in the dome lamp. The part number for the sensor is A1268301472. Usually the sensor harness is disconnected or the air hose is disconnected or not drawing air over the sensor.

Customer: replied 1 year ago.

Hi Marty, i replaced both the sensor and the blower as well as checked the vacuum line for leaks and the problem is still the same. What else could cause this?

Expert:  Marty replied 1 year ago.

Did you make sure that there is suction at the hose that connects to the sensor? With the a/c on you should be able to place a small piece of tissue on the grille of the sensor and have it stay there. Are you getting voltage to the sensor? If any of the other sensors are disconnected it could also cause the problem. What is the history of the problem? Was any work done on the air conditioning?