I have a 2007 w211 e320 diesel owned since 2015, now with 200k miles under its belt. It took me 4 years of looking for a car with the particular list of extras that it has. Having several grand kids I particularly wanted the integrated child booster seats in the back and the rear facing bench seat in the load area making it a 7 seater. The list of extras was huge however and I ended up with everything except the sun roof and the rear DVD screens. Included in this list is the 4 zone climate control (“luxury climate control option 581”), and it is this that has now started to play up.

The aircon was working fine in the summer of 2020 although by autumn it has begun to weaken and by summer of this year it had stopped getting cold at all, so I had it re-gassed and on the face of things it was working fine. However the recent hot weather served to show that actually it was not working well and so I had it checked again and was told that the pressures were fine and it must be a valve/control issue.

I have done a lot of diagnostic checking and research and I think there may be duo valves and sensor problems causing the system to be weak in general,

but always the left vents are colder than the right both front and rear. But more of this later because I have a fundamental question first about the refrigerant fill weight. It seems reasonable to assume that because the 4 zone system has more pipes and 2 evaporators, cars fitted with this option will require more refrigerant than the standard 2 zone model. However, I have searched far and wide and for the W211 I can find only 1 fill weight listed and that is 950g. On the S Class and predecessor E Class W124 I can see 2 listings, 1 as standard and a second for cars with “rear A/C”, the W124 takes 950g standard and 1150g 4 zone.

I queried this with the A/C guy and he said that he did not refer to any list but looked at the sticker on the underside of the bonnet which indeed states 0.95kg. Although he acknowledges my logic he claims that the sticker is irrefutable proof that has used the right amount of gas on my system!

Does anyone have access to any resource that would indicate that when the option was fitted the replacement sticker with 1150g was omitted!? That is my suspicion!

Any advice gratefully received however I think it reasonable to address the fill weight issue first then look at the other possible faults!?