Why does the air conditioner "howl"? Possible problems with the electronics?

Question

Electronics

After some time after switching on, the indoor unit of the air conditioner begins to "howl", as if there is a snowstorm and a blizzard, relatively speaking.
The repairman came, changed something, it did not help.
I have a suspicion that the electronics are to blame, namely the electronic board,
which is located in the external unit? Is this possible, what could be the reason and is it really possible to fix it?
Air conditioning "Whirlpool".
Thanks for the answer.

Answer 1

The usual problems of all the equipment that is spinning (fan, generator in a car, washing machine, cooler in a computer, ...) - it starts to "Howl" over time.
The reason is bearing wear.
The solution is to replace the bearings or the entire assembly.
A temporary solution is to add oil or grease to the bearing. It can help for a day, maybe for a month. Then it starts to howl again.
Your air conditioner has a turbine that spins and blows. She starts howling.