I had this problem a few years ago on my 2008 4.8 (it was about 3.5 years old at that time) and it was a combination of the refrigerant being low AND a bad final stage resistor....

i kinda have the same situation with my '08 4.8i. the passenger side eventually does cool but it takes a long time all the while there's cool air available from the driver side. it's a bmw standard story, afaik, since the driver's seat is the only one guaranteed to be occupied while the vehicle is in operation the system is designed to fail there last. so it's going to be biased toward the driver while it can't achieve full cooling power for whichever reason, in this case likely low refrigerant.

there is a DIY on youtube on an e46, reporting pretty much the same issue and how to sort it. but it's laid out differently in an e70 and i don't know which connection to tap into. still trying to figure that out before i do it wrong.

I've never seen a functional diagram of the E70 HVAC. Are there two evaporators?

as far as i can tell there's only one evaporator. i can't quite fathom what kind of magic BMW employs to bias a failing a/c towards the driver, but it works quite well.

had another look the other day and there's this aluminium block to the right of the engine that has a few hoses/pipes going in and out of it and two capped connections on the top. both those are different sizes, so you *shouldn't* be able to get it wrong when hooking up pressure gauges and re-gassing your system. it's generally recommended that you drain the system completely and refill with the specified amount, which is somewhere around 3lbs, if i'm not mistaken. simply topping up the system often leads to overfills which causes high system pressure and a reduced cooling effect.

Our 2008 X5 4.8L had the same issue the last 4 years, each year I added a little Freon. I just inserted a thermometer in the Pass side vents and added Freon very slowly, stopping frequently until I had the vent blowing good cold air. About 42 degrees when 90+ outside. This year my Compressor started making noise so I replaced it and all O rings in all the hoses. So far it has blown cold both sides and I have not needed any additional Freon. I did flush and evacuate the entire system as part of replacing the compressor.

And in the UK it is 'biased' to the passenger. Go figure...

:)

actually i don't remember. neither my E36, nor my E46 had air con issues beyond a clogged pollen filter preventing air flow.

My point is that this 'carefully engineered' feature- to provide AC to the driver at all costs- or whatever, is simply a random consequence of how the evap is designed; where freon enters; how it transits; how low freon pressure results in uneven cooling and finally how one side is directed towards the driver OR the passenger, depending on the handedness of the country or market.

I had the same issue with our E70, 2008 4.8L, every year since 2012 I added Freon in the spring and it was good for the summer but not working again by the following Spring. Always the pass side not getting cold. After recharge all was good again till next year. This year my AC pump went out and I replaced all the Orings and the AC compressor. Now all is sealed and no more additions in a year.