Honcho

Seems strange to me that hitting the "Auto" button on the Climate Control panel ALWAYS engages the AC.... even when only heat is needed.

Is the AC just always engaged to dry out the air when in "Auto"?

I pretty much always disengage the AC after punching Auto when the heated seats aren't enough for me

If I recall correctly... when I turn on the windshield defroster the AC light comes on and very hot air blasts out the vents, and that would make sense if it's to dry out the air being spewed at the windows.

Just curious if I should stop "overriding" what the CC wants to do when I allow it to decide how best to keep me comfortable.

kajtek1

AC will come on even on cold morning to defog the glass.
I also experienced the AC coming on in unpredictable time, what I took as self-testing.
This car has lot of testing programs and you just never know when something will get engaged.
Coming to AC I have it set and don't touch it year around.
Sometimes I need to adjust it coupe degrees depends on mood, but that is about it.

Honcho

So when the AC light is on, is the compressor always running?

I don't see the point of the wear and tear of running the compressor if the air is dry (enough) already.

kajtek1

If in doubt - check the manual.
MB changes the logistics from year to year.
W210 had EC(onomy) button, which when pressed, had the light on and AC was off.
A bit confusing.
Mine W211 has 4-zone with LCD display and I have display saying " ACoff "
Don't know where in Colorado you have such dry weather that you don't have morning fogging.
I am in dry California and fogging on my truck gets annoying after morning start.
Makes you really appreciating Mercedes designs that think about those things for you.
The only advise owners from dump climates have is to turn AC off few minutes before parking for night rest. That will dry the system from ice and condensation, preventing mildew.

Honcho

Actually.... Colorado is designated Mountain Desert, so it's pretty dry everywhere... especially at altitude... I'm at 7K.

I'll double check my wonderful non-specific manual again to see if I missed anything, but at this point it sounds like there's no reason to run the AC compressor unless I want drier air than what's outside.... very rare occasion!

kajtek1

Don't overthink it. Trust German engineering.
Turning AC off on the panel is not turning compressor off.
This compressor has no clutch and turns all the time.

Honcho

Acchhhh.... oh well... at least I'd be saving "wear" of the little red light!

kjb55

Turning A/C off on the panel does turn off the compressor. Sure the belt is still spinning the compressor - but the pulley is free-wheeling. The compressors use linear clutches - so you don't typically hear the usual clicking sound of the on/off clutch types.

I run the compressor a couple of times a month to keep the system active - in-between those times - if you have the system set the way you want and press "off" - the system turns off. If you press "off" again - it will turn the system on and your settings will be unchanged - that is, the compressor or A/C On (by light) will not happen. As opposed to pressing 'Auto' to turn on the system which then engages the A/C compressor.

Honcho

Ah! Thanks! I forgot the inane way that the "Off" button is also the "On" button! I spose MB though it would be inane to label it "Off/On"