The humming box sounds like the vacuum pump for the central locking system. I bet the rest of the doors are a bit slow to react when you lock or unlock the drivers door? You have a leak in the vacuum system of the central locking. The pump pulls the system down into vacuum and shuts off. As the system leaks, the pump cycles on to restore vacuum. You need to either repair the system or disconnect power to the pump. It will rapidly burn out due to excessive cycling as a result of the leak in the system.
Can't offer advice on the climate control, I'm not familiar with the 202 chassis. You don't have the center vents pointed directly at the temperature sensing grille, do you? That'll cause some erratic behavior every time.