Azeem

Hi,

Below are the readings from AC diagnostics with engine running (by pressing AC/REST button for 5 seconds)
1= in car temperature - 25
2= outside temp - 13
3=*heater*core*temp, left - 34
4=*heater core*temp, right - 28
5= evaporator core temp - 14
6= engine coolant temp – 92C
7= refrigerant pressure*- 15
8= refrigerant temp – 56C

After switching on the AC, the driving side vents blows warm air which normally takes a while to cool. The passenger side seems more cooler which is evident from reading number 3 & 4 above as well. Is this normal in MB? This is my first summer in this car so I cannot vouch for its performance over the years.

Thanks in advance
Azeem

Plutoe

The reason for your warm air is that number 5 should be 5 not 14, sounds like you have a faulty expansion valve!!

Azeem

Thanks for the response. I do have a question though, if the expansion valve is faulty then shouldn't the warm air blow from passenger side as well. Thanks
Azeem

kajtek1

Was it really 13C outside?
Repeat the readout in the morning before engine start so we can compare sensor accuracy.

PSDCampervan

My A/C exhibited same SI/SX last year. Manifold pressure guages indicated pressure low on high side & high on low side. One 350g can of R134-A w/ UV dye brought all vents back down to an icey 40 F. I replaced rubber knobs that cover presto-valves with new ones & used teflon tape to seal. System stayed cooling properly for rest of warm season but a year later eventually began getting gradually warmer on drivers side again. I did a full evac of system recently & it passed 3 hr. vacuum trial so I refilled it w/ 950g of R134-A w/ dye & OEM spec of compressor oil (can't recall exact amount of oil added but it was whatever MB WIS calls for, I think it was like 20g). Long story short, pretty sure I have a leak in one or both presto-valves in engine bay as this is only place I have ever observed any UV dye & system performs beautifully otherwise. I have been inspecting all visible components w/ a UV light & yellow lens glasses at night pretty religiously but haven't observed any dye anywhere else. Continued operation w/ freon low will eventually throw a DTC & take A/C offline(..ask me how I know) Blower will still work but pushing A/C button on control unit will result in it's LED blinking for several seconds & then turning itself OFF again until code is cleared & freon recharged.

Azeem

Thanks for sharing your experience. The car was low on refrigerant. I had filled her up today and Driver side is now cooling properly. My AC is definitely has a leakage as I recall filling the refrigerant a couple of months ago but the car was barely used during this period. Let's see how long this fill up last. I will take the car to the dealership to check it thoroughly for leakage. From your experience do you know how much refrigerant the system can hold in lbs?
Thanks again.

PSDCampervan

2.09439 lbs. (950g) of R134-A is OEM spec capacity for W211 (at least in dual system, quad might require more?) Overfilling system with too much can keep it from achieving optimal chill so be careful!

Azeem

Update - I took the car on 200 km run (on cruise control set at 130 km) with AirCon blasting at mid fan speed, temperature set at 15degC on either side. The AirCon worked beautifully with optimal chill throughout the journey. The readings on AC diagnostic mode showed 05 - Evaporator temperature at 2DegC. Previous readings before the journey of evaporator temperature were 14DegC.
I am going to check the performance of AC during this week and revert.
I don't drive the car much as the work place is on walking distance.
Any ideas or thoughts are welcome.

kajtek1

read reply #4 .
If you don't give us data, there is no base for ideas.