With the non-economy setting on with heat, does the compressor kick in? - PeachParts Mercedes-Benz Forum

jbach36 · #1 11-28-2007, 02:07 AM

You know how you have settings on the (lame) MB a/c and vent controls, where you have the ecomony setting, which is clearly with no compressor. The other 2 controls to the left, the ones poorly marked with a stupid arrow up and down, are with compressor for a/c. But when you want heat on your feet, you can't use the economy setting because it comes out only of the dash vents, right?

If you have it on the up/down arrow control, so you get air flow to your freezing feet, does the compressor kick on for heat, or does it not engage at a certain temp? I wish MB would have a simple system like the jap cars. Much easier to use.

Thanks,

Jeff 1991 300d, 114k

toomany MBZ · #2 11-28-2007, 02:21 AM

Not sure of a '91, but the other two buttons are SUPPOSED to direct the fan to floor, dash etc. With the temp wheel in the heating degree range, the compressor will not come on, but is SUPPOSED to send heat. I also think they could have done a better job designing this system.

#3 11-28-2007, 06:14 AM

Quote:

Originally Posted by toomany MBZ

With the temp wheel in the heating degree range, the compressor will not come on....

Are you sure about that? On mine the AC will run with the heat to provide dehumidification unless it is below freezing (not sure of the minimum temperature value) or set to economy.

Skid Row Joe · #4 11-28-2007, 06:23 AM

In other words, they have heat-pumps to be able to do this. Makes sense to me.......

#5 11-28-2007, 06:45 AM

Heat pumps?

The system simply runs the AC whenever it's not in economy mode to remove moisture, then it will provide heat as required to control the temperature. The heat is easily able to overcome the AC system. The system works very well when it's cold and damp, like it is in OH this week (dry/warm air with no foggy windows). On the manual system (like my 240D), you have to turn on the AC separately if you want it to run (OK, but sort of a PITA).

TimFreeh · #6 11-28-2007, 07:57 AM

Quote:

Originally Posted by jbach36

If you have it on the up/down arrow control, so you get air flow to your freezing feet, does the compressor kick on for heat, or does it not engage at a certain temp? I wish MB would have a simple system like the jap cars. Much easier to use....

The answers to all your questions are in the owners manual. Have you looked?

The compressor is available for operation any non-EC mode, but as a previous poster said it is only used for de-humidification when the heater is in operation. As I recall there is an external temperature point where it won't be used but I don't remember what the specific value was, maybe the mid 30's F?.

As far as being 'easy to use' all I can say is that my HVAC system controls have been set on "normal" (dark lower arrow/lighter upper arrow) with the fan control on "auto" with the temperature wheel on 74F for the last couple of years - and I've never had cold feet or a fogged up window. I've also monitored the cabin temperature with a Fluke thermocouple and my cabin temperature varies between 73-75F.

While I certainly admit that the system can be problematic and hard to fix I don't know how it could be much easier to use - if you have read the owners manual.

punkinfair · #7 11-28-2007, 08:59 AM

yes i agree with the above.

the acc system is beautifully simple and well engineered - provided it is working (underneath the simplicity of the controls it is quite complex, however). you simply choose the temperature you want and leave it alone. the only time i touch the buttons is if the windshield gets icy and i want max airflow, then you use the white fan setting instead of auto. otherwise the fan is on auto and the arrows button is the "both white" setting, and you choose your temperature, and never touch it. in cold weather i might move the temp wheel into the full red, above the normal comfort temperature just to get my bones thawed a bit, then back to normal comfort setting which in the winter is just on the border between the white and red zone on the wheel.

vstech · #8 11-28-2007, 10:36 AM

in my SD, the economy setting does put heat on my feet... mine is an 82 though... perhaps they changed it in yours? when I turn down the temp, (in summer...) I get cool air out the vents.

toomany MBZ · #9 11-28-2007, 10:38 AM

Quote:

Originally Posted by Craig

Are you sure about that? On mine the AC will run with the heat to provide dehumidification unless it is below freezing (not sure of the minimum temperature value) or set to economy.

I certainly could be wrong, yet I have not run into this situation. I do notice, however, at times when the heat is on and I'm driving with a steady pedal, the car will act as if something came on, such as a draw on the engine that would be associated with the compressor. As in a parachute was deployed momentarily.
Maybe that's what it is, yet I do not feel any cold air from any opening, and the assumption thing...
Sorry to mislead anyone.

Zerohour3k · #10 11-28-2007, 01:19 PM

Quote:

Originally Posted by vstech

in my SD, the economy setting does put heat on my feet... mine is an 82 though... perhaps they changed it in yours? when I turn down the temp, (in summer...) I get cool air out the vents.

In my 300D (83), EC will put heat out on the footwells when the car is cold, and once the car gets up to temperature, it slowly closes off those vents, and blows room-temperature air out of the center vents instead.

When working properly, the automatic climate controls are a wonderful thing. Set the temp, set the fan to auto, and forget about the whole thing. The only time I ever need to use the dual-white arrows, is if the windshield is frosty / foggy, and I need to dehumidify the car.

LUVMBDiesels · #11 11-28-2007, 01:46 PM

Quote:

Originally Posted by vstech

in my SD, the economy setting does put heat on my feet... mine is an 82 though... perhaps they changed it in yours? when I turn down the temp, (in summer...) I get cool air out the vents.

This is exactly how my '81 works. I love the ACC and think the manual controls on my BMW and Chevy are low rent!

Of course this is after resoldering the stupid CCU connections

Hatterasguy · #12 11-28-2007, 06:04 PM

I don't know I just leave it in EC, Auto set for about 70 and it does its thing. I hardly ever touch it other than kick the compressor on when I want AC.

According to the manual your supposed to keep it in EC Auto even when you don't really need it to keep the system working. Guess all the little flappers don't really like to sit.

Its an excellent system when its working properly, but at this stage unless you go through it its not, and most people don't.

bustedbenz · #13 11-29-2007, 11:18 PM

I can't use the two solid white arrow mode in the summer. It directs enough AC to the defrost vents to put wet spots on the windshield. Irritating as all get out.

For me, it's "Defrost" any time I want defrost (or just plain old heat, the defrost button will roast you out if you need a blast of warmth). In the summer, Double whites any time I can get away with it, the middle button when I can't. Econ in the winter when I'm just running heat.

I'm weird though... until my sunroof quit working my favorite temp setting was to run very very very low heat with the roof open when it was about 40-60 outside. That felt great. Now i'm limited to windows down, which bottoms out at 50 degrees or so.

jbach36 · #14 11-29-2007, 11:47 PM

Quote:

Originally Posted by TimFreeh

The answers to all your questions are in the owners manual. Have you looked?

The compressor is available for operation any non-EC mode, but as a previous poster said it is only used for de-humidification when the heater is in operation. As I recall there is an external temperature point where it won't be used but I don't remember what the specific value was, maybe the mid 30's F?.

As far as being 'easy to use' all I can say is that my HVAC system controls have been set on "normal" (dark lower arrow/lighter upper arrow) with the fan control on "auto" with the temperature wheel on 74F for the last couple of years - and I've never had cold feet or a fogged up window. I've also monitored the cabin temperature with a Fluke thermocouple and my cabin temperature varies between 73-75F.

While I certainly admit that the system can be problematic and hard to fix I don't know how it could be much easier to use - if you have read the owners manual.

Oh, Tim, you are KILLING ME with laughter here. How could the hvac be easier to use???? You've obviously never drove a Japanese car. Their hvac's are far superior to European cars, and marked so easily, that a child could figure it out.

With the Mercedes, for starters, they could start with controls that normal people could read. I mean, c'mon, what is a black arrow and a white arrow on the same button supposed to mean? No one knows. You have to pull out the manual to find out. What are 2 white arrows? Who knows.

Secondly, MB could have made units that work! They're LEGENDARY for lots of problems. That's why so many people drive around with tinted windows; their a/c is broken.

Third, sure, in theory, you set it and it works. But A) the a/c condenses stuff on your windshield in the summer since they didn't make the vents right, and B) running around with 74 degrees on automatic runs the compressor all the time, which reduces your fuel economy, and reduces the lifespan of what was a short lifespan to begin with; the hvac systems are crap! So I try to use the a/c only when needed. That way when I really DO need the compressor, it will hopefully work.

And THAT is how they could have made the systems easier.

jeff 1991 300d, 114k

Hatterasguy · #15 11-29-2007, 11:51 PM

Mercedes uses symbols because their cars are sold in many different countries that speak many different languages. So they use really simple symbols that are clearly explained in your owners manual. Its not MB's fualt that you refuse to read your owners manual.

Unlike American cars where everything is in English because thats what everyone speaks right?

Thats why you could jump into a W124 say in Japan and still figure everything out really quick. No Kanji in sight...