Just got a 2010 S550 this summer. It's getting colder here in the 'burgh so for the first time I tried using the heater but it isn't working. I set everything to "auto" and cranked the temp to 78 degrees and nothing happens. The fans don't ever blow air.

If I turn "auto" off and crank up the fans manually then heat comes out and the fans work. Don't know why auto doesn't work. Any ideas?

Thanks

the heat for some reason doesn't come out of the center vents in auto mode as i recall it. There is a reason (makes you tired or something), but the car should warm up.

I can't feel air out of any vents and the windshield is fogging up (even though it shouldn't under the conditions).

It turned cold here (37 F) also and I turned the temp up to 75. I could hear the fans going but nothing blowing in face. I am not sure if this is by design. This is happening on my 08 S550. I have a 92 500SEL and I can get heat through the front vents but not out of the vents behind the center armrest. Latter, I found out that only cold air was suppose to come out of center rear vents, not heat. Maybe it does this to prevent drafts. To get heat out of center vent on 08, I turn temp all the way up until I see HI and I go in and select dashboard vents on manually.

if there is no heat in all vents then the antifreeze motor isn't working, it is located under the hood in center under wiper plastic, looks like a tennis ball with 2 hoses coming out

Similar issue for my 08 S550. Problem is, up here it has been -25F, and the service center just was de-authorized. This means a 300mile trip to Anchorage to a dealer with questionable heat. Poor me.

If you have the Rear Seat package, there is a software bug (since corrected) that might address this. I had it, and the defroster would not work below freezing temps...