Ok well the w140 system has a temp sensor on the evaporator to judge how cold it is, plus two temp sensors on each heater box to judge how warm the air actually is, plus the temp sensor in the overhead lamp unit to judge cabin temp and an outside temp sensor in the air intake box, not to be confused with the sensor on the bumper for the dash display. This all makes the system work so it does rely on that outside temp reading.

Now from experience in my w140, if someone removes the air intake box,say to service the wiper system, and drops the sensor under the box versus putting it back in the box, the sensor will more likely measure the engine air temp, versus the air temp of incoming air. This makes the climate control unit think outside air is hot and then it ensures there is a slight amount of cold air coming out of the upper dash area to cool it down. Which freezes hands on steering wheel, yet air from other vents is fine. Very subtle yet real. You can use the w140 climate control diagnostics to see the values from the different sensors and confirm the readings are rational. In my case although outside temp was 10C, the sensor would say 42C, so we thought it was faulty until we discovered it was not where it should be.

In my w124 if some idiot cell phone installer breaks off the tab holding the passenger side temp sensor in the heater box and then stuffs it under the transmission tunnel carpet, the system will try to make passenger side hot by asking the duo value to open more on the passenger side, but doesn't see it getting hot in the heater box, and since overall temp goes up based on the sensor in the dome lamp it will cool down the driver side to balance. The dual temp zones then fight. So hot hot on passenger side, freeze feet on driver side. Find sensor, replacing sensor, and put back in heater box, fixes issue.