High humidity and weak tensioner

Apr 15, 2010
So for about two years I've noticed that I get poor dehumidification when my set temp of 72-75 degrees is within approx 2-3 degrees of outside temp.

I've also noticed that my idler pulley is starting to make a little noise.

Could these two things be related? Could a tired tensioner contribute to this phenomenon?

59k miles, BMW N55 435i
You should be able to tell if the belt is improperly tensioned.

I would believe that your system would be cycling more often when the outside temps and your temperature setting are that close to each other. I doubt there is an issue.
Bet you have a variable displacement compressor. When the cooling demand is low the displacement is reduced, which improves MPG. But with reduced cooling comes reduced dehumidification, and reduced heating back up, so the air entering the cabin will still have quite a bit of relative humidity.

I prefer to run in recirc with the AC on, so I don't introduce extra humidity. The recirc isn't 100% effective so it still allows some outside air in an can be used indefinitely, maybe not in your car.

I doubt the idler pulley is affecting this, it would affect the alternator aswell.