Dancia, you probably have a faulty climate controller or blower regulator. You can check the output from the controller through diagnostics. Run Test 84 and see if the output voltage from the controller to the regulator changes...
Reading Actual Values
1. Ignition to Position 2 with engine off or on.
2. Press the REST button and within 1 second press blower speed button 4.
3. The temperature window will alternately display the test step number (ex. "02 = in-car temp.) and the actual value.
4. Use the "F" and "C" keys to navigate to the different tests.
Test 02 = In-Car Temperature Sensor
Test 04 = Outside Temperature Sensor
Test 06 = Evaporator Temperatrue Sensor
Test 08 = Heater Core Temperature Sensor
Test 12 = Engine Coolant Temperature Sensor
Test 14 = Temperature Selector Wheel Setting
Test 18 = Vehicle Speed Signal (km/h)
Test 20 = Soft Top OPEN ("u") or CLOSED ("o")
Test 22 = Power Supply Voltage
Test 83 = Not Used
Test 84 = Blower Motor Voltage
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