Mercedes W221 S500 air conditioning poor cooling

[Grob]

Hi all.
I have a problem with 2007 S500 air conditiong in that it is not very effictive. I had the system vacum tested and filled with the correct amount of gas for the model twice now. No fault codes stored or current which was checked on SDS and passes all the tests. The problem is when warm say 22c when the interior fan is in auto and temp is set low and the fan spped high the evaporator temp reading is much the same as the ambient temp. Set to manual say fan setting 2 and the temperature at the evaportor sensor starts to drop towards 9-10c and the air at the vents start to drop to much the same as expected. Once the fan setting goes above 3 the temperature at the sensors and vents starts to rise again. All the vents / motors are working correctly and have been set up correctly.
So does anyone have any ideas please?

 

[AndrewOl]

Have you checked the filters?

 

[Grob]

Have you checked the filters?

I have indeed

 

[Rory]

While I imagine there's quite a bit of difference between the relatively simply Thermatic (with twiddly knobs) system in my car, and the one in yours, the problem you're having sounds remarkably similar to mine.

I'm sure I'm wrong about this, but on my car it's as if the a/c compressor is somehow linked to the outside temp - so, without ever blowing properly cold, it seems to just about manage to cope, although it's far more marginal than I would like. Several people have looked at it and regassed it, and it had a new condensor last year, but it's still the same. It's never worked well from when I bought it, at 5mths old.

 

[Gbrowncls55]

get it put on STAR. If its not the pollen filter then it sounds like a sensor of which there are many. Star should tell you which.

 

[Grob]

While I imagine there's quite a bit of difference between the relatively simply Thermatic (with twiddly knobs) system in my car, and the one in yours, the problem you're having sounds remarkably similar to mine.

I'm sure I'm wrong about this, but on my car it's as if the a/c compressor is somehow linked to the outside temp - so, without ever blowing properly cold, it seems to just about manage to cope, although it's far more marginal than I would like. Several people have looked at it and regassed it, and it had a new condensor last year, but it's still the same. It's never worked well from when I bought it, at 5mths old.

Hi
Yes it is pretty much like that, did you change the expansion valve?

 

[Grob]

get it put on STAR. If its not the pollen filter then it sounds like a sensor of which there are many. Star should tell you which.

It has been on STAR and no faults and passed all guided tests on STAR.

 

[Rory]

Hi
Yes it is pretty much like that, did you change the expansion valve?

No - I've never seen that suggested before as a possible source of the problem.