I don't know if the 5th gens have the same potential issue with this as the 4th gens but a weak compressor can cause this effect. I have dual zone AC/heat and the driver's side was warmer than the passenger side. Couldn't find any issues in the dash but it was suggested to me that the AC compressor could be weak. This means it has lost ability to compress the refrigerant to spec. I had the compressor replaced and this solved the problem completely. It is easy to check for a weak compressor as shown in the video below.
Thank you
@94Eddie for the link, while watching that video on the weak compressor, I saw the next video which was to do with the Thermostatic Expansion (TXV) valve. I had already replaced the compressor so didn't want to replace that again. After watching that video on the TXV I decided to replace that. and this solved my issues, the AC now gets cold properly and also both sides are equal temp
If anyone is interested below was how I resolved my issue
I got hold of a set of manifold gauges which helped me diagnose the issues, with the gauges connected when I put on max AC the low side would be in correct pressure, but the high side was way too low. so this kind of indicated a blockage in the system. Since I had previous replaced the compressor and dryer bag, it could only be the TXV valve. Its a pain to get at for a fat bloke
. I took the car to a local mechanic and asked him to take all the gas out for me (fair play to him he did it for free) there was only .5 lbs in the system seems there was small leak in the low port Schrader valve, so replaced that as well.
I took the intake manifold off for better access and removed the clips holding the AC lines to the body of the car, this allowed me room to move the AC lines when I unscrewed it from the TXV value. The replacement was fairly easy only pain was the access to it. took about an hour and half for a novice mechanic like me to replace the valve, don't forget to replace the o rings
Once all fitted, recharged the system and boom AC is good as new. Its funny how the symptoms indicated to a blend door issues with temp being deferent on once side when in fact it was low gas and blockage in the system.
