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Hi,
Having recently purchased a 2015 E250 I wanted to check my aircon. It was working and cooling, although I thought it could be cooler.
Using my diagnostic scanner I was looking at various readings and noticed the Evap lower temp was set to 2 Degrees and my research tells me that this should be between 3 -6 degrees. I changed this to 2.5 Degrees and I felt the air con was actually working better.
Today, I had the system checked and the recovered refrigerant was 250g, less than half what it should be, and the oil was also less than half. It should be 590g refrigerant and 120ml oil. Maybe this is why the Evap lower temp was adjusted to give the impression it was cooling OK?
The pressure test was OK, so no leaks.
Some say the ideal Evap lower temp should be 4 Degrees, can anyone help in this matter?
You can recover R134A refrigerant to know true state of fill, but you can never drain all the oil out of the system...no way.
Oil will reside as thin film or liquid in hoses, evap, condenser and dessicant drier and in compressor, which you can not evacuate ALL even using a good R134A recovery machine.
Also with only 250 grams of R134A in the system, there is not enough sweeping force to bring a lot of oil out of the system even though you use LP and HP port as recovery.
Up to 7 grams R134A loss per year if system is stilll virgin when you last drain the R134a = NORMAL.
It can be more, from other super small leaks from o-rings ( almost 10 pcs ) and the schrader valves (2)
At this point in time due to the low refrigerant level, most of your system oil will be stuck at the EVAP.
Good that you verify R134A fill level, if R134A get any lower, the compressor will burn out because oil did not come back to it enough...stuck too much at EVAP.
Thank you for taking the time to explain how refrigerant can become less over a number of years. I totally understand this and it is most likely that my car has never had the air con serviced or checked since the car was new.
I am pleased that you have mentioned that the Optimal Evap temp setting is 2C, that is reassuring.
How do you know the evap temp was adjusted? Are you saying you think someone went into the settings and changed it?
Where are you getting the 3-6 c range?
The MB manual explains to prevent icing at the evaporator the compressor is triggered to shut off when it reaches 2 c.
Also if the ac was used the car will run the blower afterwards to prevent odors in the vents. 1hr after shutting the car off and the evap temp is over 3 c the blower will run for 30 min. If you happen to be next to the car an hour after parking you will hear this.
I would not play around with any settings unless you get the information from the MB manual.
I do not know if the Evap temp was adjusted? I though someone might have gone into the settings and changed it? I asked a few other forums about the range and a couple of answers were in the 3-6 c range. Hence why I thought someone may have changed it
S-Prihadi provided a great response above, and now I think the reduction in refrigerant was normal over an 11 year period and has probably never been checked.
The system has been fully serviced and is working great. I now know so much more about air conditioning than I did previously, great video above.
Thank you to all those that have helped, it is appreciated.
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