I was just reading through the c-class owner's manual and I'm confused about some of the climate control features.

I'm confused about 2 of the controls:

1) Page 161 explains that the center thumbwheel (the one between the two center air vents on the dash) adds outside air to the air outlets.

2) The air recirculation button (described on page 167) sounds like it does the same thing. It is either activated to allow only recirculated air or deactivated to allow fresh air.

How do these two similar buttons work together?

Also, what is the point of the "auto" button for climate control. If the climate control is supposed to match the exact temperature you set...this seems somewhat "auto" to me. I guess the auto feature is just controlling which vents will be used?

 

I believe the blue thumbwheel mixes (further) outside air to the dash wents specifically, so that the air out of the dashwents are colder than the air out of other wents if you use heating. What the purpose is, is a mystery to me.

When you press the auto button, the climate control is fully automatic, i.e., it regulates both fan speed and air distribution. Otherwise only the temperature is automatic.

 

I did some initial experimentation w/ the "blue wheel" when I first got my C240. I'm not sure it really adds "outside" air, as much as cold air to the center vents during heat mode. In cooling mode, there is no apparent effect. I leave mine in the off position (blue arrow almost hidden). I think the purpose of the wheel is to let you get some cool air in the upper cabin during heating. BTW, some of us have noticed a slight whistle from the center vent during high fan operation if the blue wheel is completely closed. If you leave the blue wheel just slightly above the full closed position, this reduces the whistling noise.

The recirc button does what all cars do, it closes the fresh air intake to the cabin and recirculates the interior air. This helps reduce bringing in "noxious" odors, and maximizes cooling/heating.

As "ahost" has said, when "auto" is engaged, the system will control all functions including air temp, distribution and fan speed. Turning off "auto" allows you to manually direct air to various vents and control fan speed yourself. If you just want outside ambient air, you need to disengage "auto" and engage "EC" (economy) mode to turn the compressor off. In any event, the system will attempt to maintain the cabin temperature you have set on the dials.

 

SFC320, on your digital system in the C320 (like mine) "Auto" in the digital display simply refers to how the fan is being controlled. With it on auto, the fan runs faster or slower as needed. Notice that if you manually press the fan speed switch for more or less fan, the auto function indicator turns off. Likewise, the fan will run in "auto" mode even if you're in economy "EC" mode (A/C off), unless you disengage it.

As you probably already know, you turn the "automatic" climate control system on/off by pushing the buttons (labelled "Auto") in the vent control knobs to each side of the display. This also resets the fan to "auto" mode (see display), but you can then disengage "auto" fan separately as noted above.

I believe these buttons function differently from the C320 to the C240... The manual discusses both systems, but is not very clear to the user.

I agree with other assessments on the blue thumbwheel. As MarkL said, if you're in heating mode, and want a little cooler air on your face so you don't fall asleep at the wheel, the thumbwheel can be helpful. Can't imagine adding any untreated air when in A/C mode, however, (esp. recirc mode) so I keep my thumbwheel closed in Summers too.

You're in good company SFC320. The climate control systems on these cars are very complicated, or at least, their use is not at all intuitive to a driver.

 

Oh no , you're pulling a Tommy? Just leave the darn thing on "auto" and be happy . Just kidding, but hey, there's a manual control for fan speed, air direction and temp. Not too hard. Yeah, the digital system has a couple extra buttons like charcoal filter and the like. Instead of saying complex, I'd say M-B gave you options that you can choose to use or leave it up to the system. Most other auto systems have a manual mode (air direction) and fan control -- can't figure out why people think M-B is more complex? Saw this in some articles too. Oh well...

 

Cool, thanks for all the good info. I think the blue thumbwheel may prove useful in the winter.

 

Ok, I've got the whistle and it drives me freakin' BANANAS!

Has anyone had it fixed? The only thing I LIKE about it is it sounds like a jet engine when the fan speeds up or slows down All the other times I just want it to SHUT-UP!

 

I agree. I think, once you figure it out, the system is very functional and logical. The auto works very well, and if you want you can control the airflow very specifically.

I guess that's why I never figured out the purpose, here in Honolulu

 

Sorry, I'm going to have to pull a tommy here, and restate the obvious: there should be a way to control EVERYTHING manually, which this system just doesn't allow. Ok, now I feel better, thanks for listening.

 

try to move the wheel a little or something like that... don't have it at the extreme end. let me know if that works...

 

Like young said, if you move the blue wheel up just a tad from fully closed (down) the whistle should stop. And, at that position, you should only get a very small amount of cool air from the vent during heating -- not enough to be annoying. I think I only heard the whistle when the fan was running at a pretty high speed. To test, just set the thing on manual, direct air to the floor vents, jack up the fan speed and try the blue wheel until the whistling stops. Good luck.

 

Also, when the system is in auto, it will do creative things with directing the air that you wouldn't normally do yourself to keep the cabin comfortable. Like, after initial cool-down, it will direct part of the air to the defrost vents to spread out the air flow (you can hear the very slight "click" of the vent opening, and the difference in air sounds). Also, mixing air between the floor, upper vents, etc. IMO, it's one of the best auto systems I've had.

 

I had to play with this to stop/reduce the whistling. It does work. Of course, so does turning up the radio!

I like the auto system very much. Once you get it figured out, it's not really that difficult. I normally have the auto control on the fan, but I leave the vent selectors in manual mode. For some reason in Auto it was directing too much cold air on to the windshield causing them to frost.

 

Yeah, I knew about leaving the blue wheel open a bit to stop the whistle, but I'm not satisfied with that solution. I don't think it should whistle in ANY postion.

 

I agree. MB better fix these types of problems before releasing a product. I have a C43 and I just started hearing the whistling sound when the AC is in Auto and full blast. I freaking hate it. I just had the compressor and transmission replaced and I'm not looking to pay for another repair. The AC is cooling so it's cool for now.

 

my family members like heated air blowing on their face am i the only one that hates it?

 

I agree with Revstriker, I have to shut off the Auto function every morning to keep from fogging up the windshield. I am disappointed that M-B did not remedy this before going into production.

 

I am very confuse. So for the center knob, is it more blue = more outside air entering the car or is it the other way around.