My car is just coming up to its third annual service. On two so far isolated occasions. Very warm air, almost of the make- you- sweat variety has pumped through the vents, even though the heater was off and the AC was on with the temperature set at minimum. The last time The car had been parked for two hours after an under two miles trip and the heater had been on for about a half minute to vlear some misting and then turned off. Can any suggest what the problem may be and a solution, please? I would like some idea before I go to the dealer.

I think it's possibly the flaps which redirect hot/cold air need resetting. If that doesn't work I think you need a new control unit - have a search, it's quite a common problem

Chris