Automatic Climate Control
 

I feel embarrassed to ask, but don't have my manual with me and on a trip. I tied finding a manual without success.

Is there only one setting for defrost? It was blowing high and hot which makes my eyes uncomfortable so turn it off, then wait until it fogged to turn back on. Even tried turning the floor vents on to keep the cabin warm, but...

How does one get the automatic mode to work? There is no light that comes on/goes off, and even with the temperature turned down, the heater doesn't go off.

Thanks in advance! :D

On my 126 the defrost is always on max blower and heat when selected. When set for economy heat the leg room vents are open and there is a small flow of air to the defrost, at the selected heat temperature.
If you do not have any warm air flow to the defrost area when in the heat mode there may be a problem with the vacuum pods in the heater.

Thank you for the help! :D

So with economy, the automatic climate does not work? So then set it to normal then?

Next time I use her, I will see if I feel warm out the defrost. The pods were replaced, so should be fine.

I'm not certain I am following this exchange, so here is another $0.02....

When defrost is selected, the system should operate at full heat and highest fan setting out the defrost vents only. There is no auto temp control and no way to reduce the heat output. That is how the system is designed.

In all other modes apart from defrost, you should be able to choose between manual control of fan speed or the auto setting, which operates the fan in concert with the auto temp control. You should also have auto temperature control, based on the setting of the adjustment wheel. Economy mode only differs in that the AC compressor engage on that setting.

In every other mode other than defrost, if you are selecting a temp and the system isn't shutting off when that temp is reached, there is an issue with one or more components.

Zacharias, thank you so much for your help! :D

So I am doing something wrong. How does one know when they are on the automatic setting? What does it control, fan speed AND temperature?

Sorry, when I read the thread the first time I thought it was you who mentioned a w126. I now see it was the other respondent.

You always need to specify the model and year of car you are asking about.

I doubt you are doing something wrong. Assuming for now this is a w123 or a w126....

When you
1. push any button except defrost or 0 (off) and
2. set a temperature setting on the wheel, and
3. push the middle button on the fan speed controls

The system should maintain the selected temperature (fan speed will increase while the interior warms up, then automatically slows when the selected temp is achieved).

If this is not happening, there is a fault somewhere in the system.

In fact, the air conditioning compressor engages in all operating modes except Economy.


The ACC does not "shut off" unless the OFF mode is selected.

1. I meant to say "does not engage"

2. I think my post #6 clarified what I meant when I said "shut off".

For some reason missed the reply... Thank you all for the help! :D

Zacharias, sorry I forgot the information was not available. I am used to it being in the signature, which I apparently forgot to put. F.Y.I., this is in regards to a W123, specifically a 1985 300TDT.

What I am doing wrong is assuming once the desired temperature is reached, the system shuts off. Instead, it only slows down the fan speed. So, automatic only means automatic fan control, rather than full temperature control?

Again, how does one know they are in the automatic mode? There is no light like the other buttons that I can tell...

So why would the compressor turn on when heat is selected?

As far as I know, there's two reasons why the AC compressor would run even during heat output --- one, the air is probably still pretty moist (even if its cool out) and you dont want to put hot moist air on a cold windshield, and two it keeps the compressor lubricated so the seals dont dry out, leak freon and become a engine christmas ornament like mine is right now.

I would not expect the compressor to act as a dryer, but if so, that is quite fancy! Good to keep in mind if one is trying to make it to the next station! ;) :P

Too bad about yours, but good to know they can dry out. Mine is brand new, so hate to shorten its life. ;)

That's the way the system was designed. If you don't want the a/c on, push the EC button.

That is precisely why the a/c runs in the defrost mode. More precisely, the drying occurs at the evaporator, not the compressor.

I don't mind, just want to understand. ;) This system is quite fancy compared to even modern systems like my Grandmother's 1980 Buick. All it has is automatic temperature.

What I still don't understand is how does one know they are in the automatic mode?

If the system is working properly, the fan will stay on all the time, as you mention.

The push button you select will be brighter than the other buttons.

These units fail, so if you make a selection and nothing happens, after a delay, then it isn't working.

Thank you! So then, maybe the light is out? The system has been gone though, so thinking I must be doing something wrong...