Climatronic Error Code 04F7: Diagnosis & Troubleshooting

Hello everyone,
Today, I performed an actuator test on the climate control system of my Golf 4, manufactured in 1998, with a 1.9 TDI engine and 90 horsepower. Afterward, I received an error message: "4F7 Temperature flap actuator motor."
Before operating the vehicle, I noticed that the air conditioning system alternates between cooling and then apparently letting in uncooled outside air into the car's interior. Today, with an outside temperature of 26-28 degrees Celsius and moderate sunlight, I had set the desired interior temperature to 18 degrees. However, my subjective feeling was that 18 degrees were not reached, so I started the diagnostic mode. During this process, I observed the following:
Channel 1 displayed a reading of 28 degrees; I don't think it was actually that warm, though.
Channel 7 displayed a value of 35 degrees; why would you blow 35-degree warm air into the footwell of a car that is already 28 degrees warm, when you want it to be 18 degrees?
Channel 8 displayed -51 degrees; I think that would have caused the plastic of the nozzles in the dashboard to freeze if that were true!
Is it the software of my Climatronic that's malfunctioning, or is it actually related to the defective actuator motor? Or is it just the potentiometer on the motor, since it's producing both warm and cold air?
I hope one of you can help me! Thank you in advance!