A couple of months ago I replaced a defective temperature control on my Kitchen Aid fridge/freezer. It has kept temperature properly ever since.

Now, the fridge/freezer started making a buzzing noise. I opened the rear access panel, and confirmed that the compressor is kicking on and the fan is clean and running properly. The noise seems to be coming from the area where the water supply enters the rear of the fridge. The ice maker tray is full, and the cold water dispenser is dispensing cold water.

The unit is freezing and cooling properly and the buzzing noise is not coming from the compressor. What could be causing this annoying buzzing noise?

Thanks,
Sup