Sara Picasso air conditioner problem

I have a problem with the car air conditioner, I do not enter the air with force, occasionally and with the vehicle brand, it enters cold or hot air (discarding failures). As they told me, the problem can be in a resistance of the electro -ventilator, but it is taken to several mechanics and have not found what is causing me not to work the electro -seasons. I listen to your opinions, thank you!

You could check if the fan is not obtracted with dirt that stuck the blades