Aircon stops cooling AND fan virtually stops blowing anything

After about an hours driving with the aircon on cooling (this was in the summer, not during the recent snow), it suddenly stops cooling, and the fan virtually stops blowing any air at all. Once the aircon stops working, setting the fan speed to max gives less air flow than the normal min setting. Fan makes all the right noises just does not blow any air on any vent setting. I use it in manual mode (auto and dual zone both off).
Many thanks.