Don1954

New owner of 2016 S550 with 18,500 miles. I quickly discovered the AC does not cool properly. Does fine for about an hour and then gets uncomfortable.

Dealership checked and advised, "No faults were presented. Works as designed. Must be operator error."

Any thoughts?

I've never had a car with such lousy AC.

Quite disturbing to say the least, especially living in New Orleans.

Thanks in advance for any thoughts and ideas.

Mitch Alsup

Works at first, then diminished capacity later on is a sign of the Expansion valve being partially logged.

Don1954

Partially logged? Perhaps you meant plugged or blocked?

Is that something I can handle or is it shop time?

And thanks for the reply Mitch!

tkelley.EClass

Must be an issue. It can 100 degrees out and after a few minutes I have to turn down the A/C as the cold air on my bald head gives me a headache.

Mitch Alsup

Partial clogging can have to do with tiny particles from the seals on the compressor, or from tiny amounts of water vapor in the system icing up after a few minutes (my bet).

It is probably "not that hard" to get to the expansion valve--they are serviced rather regularly.
However, you are supposed to evacuate the "freon" before removing the EV and the refill the system after the new valve is in place.

Don1954

Thanks again Mitch! I shall venture to a different dealer and try again.

obwielnls

When it stops cooling does the air flow seem really low? LIke it's blowing hard but no air is coming out?

Sal Collaziano

The only place where this is an issue in mine is the back seat. There's not enough airflow back there...

Newbie2015

This is probably the problem with my air conditioning. I actually had small ice particles come through the ac vents. At least now I know what to tell the dealership.

obwielnls

Likely low on freon and freezing up.

Don1954

No, the air still flows. No blockage thru vents.

Don1954

Low on freon means system has a leak.....

obwielnls

That's true but over time all automotive systems leak a little freon. The seals near the spinning part of the compressor will seep a little gas. A perfectly functioning will really need to be evacuated and charged properly after some number of years.

I purchased a W221 body s-class from a dealer that said the previous owner had traded it in because of some AC issue. The dealer told me they never could find any fault at all and it worked fine. As it turns out it was low on freon. It only was noticeable on a long road trip where the interior of the car was able to cool down and stabilize. At that point the low freon caused the evaporator to freeze up. It took me a couple of times to figure it out. I evacuated all the freon (it seemed to be about 1/2 full) and recharged with the proper weight. The AC never had any more issues and I never had to charge it again over the 5 years I owned it.

Don1954

You sir are a gentleman and a scholar! I think I shall try the evac the old Freon and put in new.

Thanks so much for the assist,from you all!

konigstiger

See attachments for recharge.

Don1954

You Konigstiger are exceeding expectations. Thanks so much for the how to's!!

My 550 is still under warranty so I took it back to dealer yesterday and advised them that the poor AC is not due to my ineptness. I just picked the car back up after they said they determined it was low on Freon, evacuated the system and replenished with proper weight, adding dye and discovering no leak.

It is funny your how to came in the same day the repaired it.

Thanks again for this kind effort!

Stephen513

Hello,

I just had this same issue with my 2015 S-550... had to take to the dealership twice. The first time, they refilled the freon and returned it to me. The same thing happened. Took the car back, they kept it for 2 weeks. They ran the car all day long every day to figure out what was the issue. They never found what was the problem, so they ordered a whole new A/C unit from Germany. Two days into the new system, all is well. However, I will happily take the car back and have a loaner for another two weeks until the problem is fixed. It should be 100% covered under warranty. My recommendation is to continue taking the car back to the dealer until the problem is fixed. Hope this helps.

Don1954

Wow! 2 weeks running it every day.....I hope yours is operating as designed!
Thanks for sharing that.

Don1954

Good news here, the dealership repaired the AC! They determined the unit was low on Freon so they evacuated and filled to the correct weight . Works like a charm!!