I just bought a 280CDI that is either an '07 or 08MY (manf date is Aug '07, but was CKD'd and reassembled in India - so not sure if this is an '07 or an '08).

The AC was not cooling properly so as a quick fix, I had the refrigerant topped up. It does cool, but not as much as I expected it to (I compare it with my '04 220CDI) which cools me down easily even on the hottest days.

Today I had a local independent MB tech check out the error codes -- there were none. He ran the self test and also re-initialized the flappers etc. No errors.

But, the min temp we can out the center vents is only 9C (measure in Lo with low fan speed) vs. what I was told (by another tech) should be 5-6C. The evaporator temp is at 1C and the system pressure is 13-14bar.

I just made some measurements:
Ambient 27.5C, Interior 28C
Set at LO/lo fan speed -- center vent 9C, side vents 16C (I think rear vents were a bit higher -- don't remember)

Set at HI/auto -- center vent 26C, Side vents 33C (again don't remember rear, but it was similar to side vents). Air output from center vents was lower than from the sides.

When I started it earlier today while returning from a short errand trip, the air out of the side vent blew hot for a few seconds before turning cool (but not cold enough vs. my expectation)

I read thru the Changeover valve thread, but not clear to me whether it is an issue here. More confused cause we did not see any error codes.

Appreciate any help in troubleshooting this.

Thanks!
Byas

 

Your indy must be a snake charmer,because there are loads of AC faults if you have the correct diagnostic equipment--ask him just one question---Did he use DAS Xentry when he reported no faults!!---now if he responds with flute like sounds then slowly remove youself from his presence and find someone with the diagnostic equipment---less you will be running around the May pole!!

 

I'm not sure what it's called, but it was an MB branded box that was plugged into the car and to a Dell laptop running MB software. Isn't this the STAR system? He was with Mercedes Benz India before leaving to start his own shop. I was in the shop floor with him when he ran it and checked for faults.

Byas

 

I've had a failing part not throw up an error before -- a thermostat in my '09 C300 in Sacramento which seemed to me to be failing as it was taking much longer to warm up, but Von Housen MB techs didn't find any faults. 2 weeks later it failed open.

Was wondering if the same thing was possible with the changeover valve or something else in the AC system where it is not working as it should be but not yet triggering the fault codes.

Thx,
Byas

 

Well you are correct Star aka DAS Xentry Diagnostic equipment---what is amazing is that the AC is not preforming to spec and yet there are no faults---has he put a set of gages on the car to determine the high and low refrigerant pressure!!

 

Beside spammers who will tell you "you need DAS in Florida to change light bulb"
you should be able to do some work the old-fashion way..
Center vent is design mostly for delivering fresh air, so it might not be the best to measure system performance.
1C on evaporator is excellent, but was in on both?
13-15 bars if was taken at full output is low. Recheck the pressure when you restart car sitting on sun for some time.
I assume you have to be in hot place, as even in CA we rather use heating than AC

 

"Center vent is design mostly for delivering fresh air, so it might not be the best to measure system performance.
1C on evaporator is excellent, but was in on both?"


Total misinformation--the center vents are designed to provide the cooled air----15bar is acceptable on high side and 4C is an acceptable value for the evaporator

Be watchfull this gent is known for much mumbo jumbo, confusion and misinformation!!

 

I gathered a bit more info today.

Outside temp ~30deg C
Interior temp ~34deg
AC set at 23C, Auto, center vent air is 15C, Evap at 3C, 15bar
AC increased to 25C, Auto, center vent air is 27C(!), Evap is at 4-5C, 15-16bar.




AC at 22, Auto, center air = 11

AC set to Hi, Air stop coming out of the center and comes out of the defrost (even though I've set it the rotary control at top vent setting) -- moving it down one click and putting it back to top vent setting brought the air back to center vent at 44/45C.

Will sit with the tech and check blend flap positions at each setting. Anything else I should try?

Byas

 

As I said, 15 bars is low. Be very careful with adding refrigerant as at this level small addition will make big pressure change.
Cut off switches are about 32 bars so you don't want to go there, but I wold like to have at least 20 bars.
The defrost is default mode for flaps. I am still learning this model, but on old vacuum operated system that would mean loosing vacuum.
Than if you park car directly on the sun, the computer will divert air per sun sensor readings.

 

I got my '04 E220CDI back for a comparison. The '04 cools brilliantly. I never have to set it below 25/26C when it's 30-35 outside.

On the '04: With the control set at 25C on Auto, interior at 28, the Vent temp was 13C, pressure was between 10/11 bar (!). The pressure and evap temp readings are from the hidden AC menu. (05 for Evap temp, and 07 for bar). So, the lower pressure level clearly did not hamper the cooling. The cooling was actually better than on my '08.

I'm thoroughly confused!!

Byas

 

Variable output compressor confuse even professionals who got used to old on/off compressors.
10 bars on car that is already cooled sounds right, but you need way more when the car needs cooling.
So once again, important is number at full output, what you can measure when you enter car with cabin above 30C and start AC.
I do have climatronic who allows me pressure reading with push of couple buttons. My best way is to enter hot car, display the AC pressure, than start the car and observe how pressure fluctuate.
Right after the start the pressure usually go to 28 bars, than drops gradually till it stabilize when the cabin cools down.
The pressure also slightly change when you let the engine to idle.

 

I did what you suggested. AT lunch today, I tried again. Car was sitting in the sun and hot inside. I turned key to second position, displayed AC codes and then started the car. Internal temp was 35+C, AC set at 23C. pressure hit 17 bar briefly, then dropped to 16 and down to 15.

Car still cools well at 23C but blows out warm 28C air when set to 25C. I also feel there is a smell from the AC. Perhaps low pressure plus a leak? Fungus?

Byas

 

17 to 15 bars is still giving some cooling, but not enough to cool down 35C cabin in couple of minutes.
Could you read evaporators temperature, that would confirm.
Usually when refrigerant goes low, one side acts faster than the other and that can create quite a havoc.
Replacing old cabin filters is always good idea

 

When control was set at 23C, evap at 3C, pressure peaked for about 2 sec at 17bar before dropping to 16 and then 15 and finally 14. Vent temp was 16 to 17C, interior temp was 33+

Same interior temp, control set to 25C, evap was at 5C, pressure at 14-15, vent temp at 28.

Same interior, control set to 24C, vent temp at 18. Its very strange to me that shifting from 24 to 25 drives vent temp up by 10C. That does not make sense to me.

 

I think what you are missing is fact that computer changes lot of things base on sensor readout and you can't see what is going on in computer mind.
First fact is that when computer sense core temperature raising due low refrigerant - it will set the blower to lower speed.
The temperature inside the core will be still the same, but there will not be much of cold air.
Just for the sake of that you can repeat the test with blower set manually to max.

 

I took both cars to the dealer and showed them the difference in cooling. The '04 would vent out air at 10-14C when set to 25C while the '08 would put out 25-28C air at the same setting.

They checked out the '08 ran full checks on all components and compared with couple of other '07s and '08s that were there. Their conclusion is that my car is working to spec. They could not explain why the '04 cools so much more, other than to say t is an older car. (It does have a slightly different system to be fair with an additional temp know between the 2 front upper vents).

Byas

 

Did they also measure the air flow?
I will repeat one more time that you have low refrigerant pressure.
Full test would take reading low pressure at the same time, but I think that $6 spend on a can of R134 would be money well spend.
Can might be even too much, so do it in 2 stages while measuring the pressure at max output.

 

I'm not sure about the air flow. I think you are right about the refrigerant pressure/volume. The dealer said the only way they could check would be evacuate and fill 850g. Is there another option? Can they fill to 25 or 30 bar -- since it is a variable compressor, how would they know that they are not overfilling?

 

They are right that the only guarantee way is to start empty and fill up by weight, but I had intermittent leak on W210 and dealing with it for few years made me an expert
As I said, add 6 oz and see if you can get at least 25 bars.
Overfill would make >32 bars, what has limit switch on W210 and I assume the same on W211 so even if you do that, it will not destroy the system.

 

He is running you around for nothing---- 25 bar is an overfilled system and way to high---be very careful!!

 

The service tech mentioned 850g as the amount of refrigerant. Is that the correct quantity? I'll probably have them evacuate and refill. Not the dealer, but have an indy shop do it.

This was the reading from the dealer btw. Not sure if it adds any info.

 

No------your 211.020 total capacity, repeat total capacity is 950g and be very careful of the less learned that say otherwise.


I think you are extremely confused---if you look down at the bottom of the page you will see the file name\path----that is rarely given to customers-----that is the location within DAS for the test and the results are useless unless you double click on the value and it will refer you to an understanding of the data.


The folks that in the future who read this thread will be so confused because of all the mumbo jumbo misdirection and misinformation--it's a shame!!

 

Now you have to choose who do you believe.
MB technician or known forum idiot.
Simply fact is that refrigerant charge is always listed on the car. Might be on compressor itself, or on a beam under the hood.