The air conditioning regulator does not work for me

Hello, I would like to know if anyone knows how I can solve the following problem:
when I try to regulate the air conditioning, it does not work, it only works when the wheel turns to the number 4. What can I do?
The vehicle in question is a Scenic of 1999.
Thank you.

Look usually the speed resistance is damaged. This model manages a mechanical one. What is genically damaged is a diode that goes in the resistance, a bridge is in the diode and the four speeds will work again what the resistance passes manages the first three and the fourth is direct of the control of the A/C to the blower motor

It is correct what Gaudencio says05, the fourth is direct and in all models and brands when this happens is the fault of the rule or change or the bridge is your decisions

Thank you very much Gaunndencio and Kikemec but if I punctuate the resistance will continue to function the different types of air speed?

It is worth now I understand it, taking off the diode and strucking it, I will work for me, but can you say where they are? Is it that I am a bit lost, that they are in the same incorporated speed regulator?