YAP

My AC is working cool every day.
I don’t feel anything bad in a hot day.

However, I can’t turn off the compressor by turning off the AC button after started working.

Even though I turned off the AC button, cold air could continue.

I had to stop air conditioning system once by using OFF button to stop compressor then I had to restart blow again, even if I just wanna stop only AC and if I still need natural temps air circulation.

I don’t know it’s a problem or normal.
Does anyone know what’s the reason?

Thanks for helping.

S212, E250 -2010.

DFWdude

After turning off the A/C at the button, it will take several minutes before the air blows warm. Turn it off and wait...

YAP

Thanks, DFWdude.
I tried check it according to your advice.

Since I activated A/C, then I turned off the A/C button.

Cold blow continued several minutes then it turned to warm actually like you mentioned.


1st try
It spent 6 minutes.

2nd try
It spent 1 minute.

3rd try
It spent 4 minutes.


Are these results correct?

pierrejoliat

That's how mine works, Takes awhile to decide to turn off, but does eventually.

DFWdude

Pretty much, yes. In the Spring and late Fall, I like to run the car with fresh, outside air rather than A/C. It takes minutes to get the ambient air flowing. Works the same on my earlier C320, too.

bmwpowere36m3

I noticed this as well... however experience with older cars including MB is when you switched off the A/C is was nearly instant. So I suspect on this car, when you toggle the A/C the controller has logic, so its not a direct switch (more input). Maybe its related how long the compressor has been running, temps, humidity, minimum time running since its compressor cycle, etc...

nota_amg

Also, I don't think the AC compressor has a clutch, so it takes time to complete the reaction and warm up the evaporator by opening the orifice valve...at least that's how it worked in the early 2000s. Had an SL compressor lock up and it blew out the rubber coupling where the clutch usually is to allow it to free-spin separate from the compressor shaft. And that is the only AC compressor replacement I've EVER done on a Benz...

YAP

Thank you guys.

I am a beginner. This is first post.
What an interesting discussion.
So, double thanks.

I guess SAM controls it but it seems buggy in my feeling.

Anyway,
When I’d like air blow (no A/C) ASAP, instantly, immediately, we have to do next 3 actions.
-Push “A/C” (light off)
-Push “OFF”
-Push Any button except for “A/C”.
It does not seem smart but I don’t wish to wait several minutes probably.

And also do you guys think that this order is not good for the system protection?
If the computer was programmed to protect compressor or something....but I don’t know.
Should I wait several minutes rather than above 3 actions?


By the way, Do you guys think that the waiting time can be changed since some reasons about refrigerator gas or oils refills ?



My low pressure is 38 psi (while idling). I think it's bit lower in medium value. Probably 45-50 psi would be better, I guess.
Although I don’t have any gear to measure high pressure valve.

Arrie

The easier solution for getting non-cooled air in the car is to change your temperature set point up for those 5-7 minutes that it takes for the evaporator (cooling coil) to warm up again after compressor shut down. Then you need to change temperature back down after cooling is lost...

The rather long time it takes for the cooling coil to run out of cool I think is to serve cars with the ECO engine START/STOP. If the coil would instantly loose cool it would mean ECO START/STOP would never work in warm climate as A/C would be lost for any length of engine stop.

DFWdude

You might be on to something with this, Arrie. But I recall my dad's 1970 Buick LeSabre, where it's A/C blew cold air long after the Off button was pushed.

A/C does so many things other than simply cool a car's interior. Turn on the windshield defroster and the A/C starts automatically to dehumidify the air hitting the windshield. It's been that way for decades (long before ECO Start/Stop). There are other examples. But yes... serving ECO Start/Stop functions might be just one more reason (among dozens?)

In today's "LUXURY" cars, it's presumed that the owner will let the "Climate Control" unit run automatically, all the time. Hence, I'm not convinced that Luxury cars are engineered to run without full-time climate control. Heck, my 2001 C320 does not even offer an "OFF" button for its A/C. Instead, I select the "Rest" button and wait several minutes for ambient air.

So, on the occassion when A/C is not needed, I think today's luxury car has to complete several steps to shut down, which is against the norm. I've driven my share of econoboxes where the A/C immediately ceases when A/C is "deselected." Not so at all with upmarket, luxury models... of the same era.

YAP

Some makes sense.

I still wonder something.

-Push “A/C” (light off)
-Push “OFF”
-Push Any button except for “A/C”.

When I did this order, A/C could stop instantly.
I can hit a natural temps (no AC) air in 2 seconds every time.
It's an easier solution than the solution what Arrie mentioned on #9, I think. (Sorry, and Thank you so much, Arrie).
But I am worry about this solution due to the unknown reason of this system.

When I just turned A/C light off, then I was putting my hand on the center vent while waiting 6 minutes to notice the turning point of actually AC off. The turning point was so clear. That’s not crossfade.

I hope to know the reason and criterion about these additional time.
6 minutes was very long even though I had used AC for only few minutes before the action.
And the timing is not same every time. Sometime 1 minute, sometime 4 minutes.

I thought this is a trouble so I opened this thread.
Now I know there are some friends have similar issues but I don’t know all guys are in same condition.
I also wish to know the average time to stop AC actually since AC light off.

Arrie

Both of my cars, the E550 and S550 do the same thing. When I drive and just hit the A/C button to turn the compressor OFF it takes 5-7 minutes before it stops blowing cool air so I'm sure the systems in these two cars are built to work like this. Perhaps it is the "heat" recovery system, or in this case cooling recovery system to use up the cold load from the coil that was made to it by the running compressor?

When you turn the system OFF and then start it without A/C running then it probably skips the recovery part as the compressor was not running first and adjust the air mixing gates so it does not pull cooled air from the evaporator coil?

Just trying to guess how the system works but I'm sure there is nothing wrong in yours.

YAP

It’s a great report for me.
Thank you so much !