If I have the aircon on and the car isn't moving forward, as in traffic, then hot air from under the bonnet is pulled into the heater box, so even with the heater fully off it can seem as if it is on. As soon as the car is moving the cold air returns. I need to re-fit a new foam seal between heater box and bonnet: I did this on the Roadster and it made a big difference.
Overall the aircon works quite well, especially hood up when, with the heater on as well it keeps the inside of the car dry. As there is no temperature sensing feedback the co-pilot has to continuously adjust temperature and fan speed to keep a steady temperature....!
