Alex, per the owner's manual (and my personal observations) , you shouldn't get *heated* air out the vents. When the system decides it's warm enough inside and/or you lower the temp setting (cooler), it may let some lukewarm air out the center - not necessarily outside air temp, but still not hot/heated air. It's a complex system, that's for sure! I always assumed the desired temp setting was the number in the middle of the dial, but honestly I just move the dial to get the air temp I like and ignore the numbers most of the time!

And - lol - no, this should have nothing to do with the infamous OM603 head problem! There are enough of those already - just heard of yet another one this week on the MBZ email list.