Hi folks. Car (VW Golf) developed a fault where after driving an hour or couple of hours (usually long trips as it won't happen in the short city distances) you can still hear the ventilation fan going but no air coming out of the vents. Turn fan off for ten minutes, all work again. 

I suspect it's a duct that's blocked or one of the flaps is broken/under pressure. Took to a garage that says looks at air con systems but the guy turn the fan on and declared "no fault" because it worked - despite the problem description I gave and mention that the fault only shows up after sometime.

Looking for recommendations for good, smart folks in Wellington/Petone/Porirua that can look at the air con system as a whole - not those places that only re-gas and nothing else (although I will ask for re-gas at the same time).