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thefisch

As the inside air is getting cold there is less heat to remove so the low side pressure will drop. Some drop is normal during operation. More heat means higher pressure. Big drops in low side pressure could also be a sign that the txv is bad which can result in uneven cooling across the evap coil. But given the even temps between driver and passenger side, it doesn't seem like you have a difference between the sides. The side vents have a longer throw so they can differ in temp from center vents with a shorter throw.

Full disclosure - everything I learned about AC is from reading on internet forums so I am by no means an expert.

KEY08

^ What he said, and has taken me to school. Your temps seem good to me. I thought 50-55 was a good temperature base sign.

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thefisch

Those charts consider ambient air as the intake air that the ac system will be cooling (i.e. the cabin temp at the start of the test or the temp of the air being drawn into the system for cooling). So the warmer the intake air, the more heat there is to remove and, as a result, the higher the pressure will be. Higher temp equals higher pressure. Normally those tests say that they want the car to run on max ac for some period of time like 5 minutes. I would check the manual on the test kit.

In regards to possibly adding more, I would be careful as you can overcharge the system. I would wait until there is a problem that is clearly evident. These auto systems with all their sensors don't always get the comfort exact. If you think the system is underperforming while you're driving, I would adjust the temp and fan speed yourself (taking it out of auto) so that you can get the response you need.

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kajtek1

http://www.mercedesmedic.com/ac-air-...le-codes-list/
Here is everything to troubleshoot the system. You already check for no codes, so now read the sensors (the link shows it on climatronic, but you need to use scanner on your model) and post the results here.
Read note on the site when to take the readings.

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Kajtek, I was trying to get those readings but could not figure it out on a 2011 E350. My scanner is a Bosch bought at Autozone so maybe it isn’t capable? Thanks! Craig

kajtek1

Getting scanner that reads everything on W212 is not easy.
I bought iCarsoft MBII this year and when it does tests and programming on W211 that were available only on SD before, it does not read some modules on W212. Don't remember if I could access AC and if I find more time, I will check it later. So if your scanner can't read sensors, you need to go to a shop who has one that does.
On the other hand the "hidden menus" on previous cars took some time to get discover and I wonder if going into engineering menu you might read the sensors on your command center, or AC display.
I hate dealing with software so will not go there unless life forces me to.

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Edward993

To the OP,

Please say that you have the proper gauges and know-how to read the high side, the low side, and make the proper adjustments according to your readings. Please tell me that you're not just doing the old "Pep Boys method" of buying a can of refrigerant (even if it is the right one) and fillin' her up. Diagnosing/addressing AC requires proper understanding of the system, and damage can result from fixes that used to work on an 84 Accord are applied to modern-car HVAC. And if you know all this, forgive me and press on!

Edward

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Arrie

Do not over fill the system. It will stop cooling or at least performance goes down. You cannot fill it by the "normal" pressure reading method with a can equipped with gauge that has adjustable scale for ambient temperature. This will result over filling it. A sign of over filling is the fan in the front starts running at very high speed.

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kajtek1

Having high pressure sensor in the car you don't need the gauges. I mean it is not bad thing to have them for advanced compressor testing, but even having AC filling gauges, I rather used car sensor than tap into high port valve, what opens possibilities for leaks.

thefisch

Is there a way to get reading off car sensor?

Edward993

Kudos to you for the DIY approach ...how I've lived for decades. And it sounds like you're savvy enough to get the info and read up. All I am saying --and cautioning about-- is that some systems are more "particular" than others, having narrower operating parameters, while others are more forgiving, even allowing for a modicum of error, and have low consequences if one messes up. As already posted, AC will not blow cold if pressure is too high as well as too low; not to mention is a high-pressure system that needs to be heeded carefully. Tread carefully is all

Edward

LemonSqueezy

No idea in detail how a/c works but have you tried a simple evac and recharge to the system? Sometimes that's all it needs. On my w211 I once had I think my heater control valve and one of the actual valve flaps go bad as well, which sounds similar to this issue in a way

kajtek1

Point is that you can do full troubleshooting in the matter of seconds once you get proper scanner. On my W211 I replaced climatronic with one that can read the sensors, so I can do troubleshooting at 75 mph.
Why drop parts/refrigerant blindfolded?

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