Hello, Did you get this fixed ? I have had the same problem for about a year now.
It kicks in either after 2 hours driving - aircon goes limp and blows next to nothing, even when manually 'forced'. It's rubbish. It'll be fine the next day.
OR, it comes on when the EML flashes on with a misfire on all four cylinders (After 30 minutes today) that doesn't exist (I'd ideally like to find that fault and fix it too !)
So far, I've dropped a lot of money on inspections with specialists and VW Dealers. No fault codes are recorded anywhere and they can't find any physical faults. It's been serviced, regassed, new filters, run for hours, you name it.... none of it finds any fault. But it doesn't work after a while. I drove the car today (it's my wife's) and it wouldn't even clear the mist caused by our breath off the windscreen..... and I know that tomorrow it will blow brilliantly.
Damned annoying. And the attitude of the dealers is the usual - no sir, no faults recorded, there's nothing wrong with it - the computer says so.... - so any guidance/solution you found would be fantastic.
Thank you.