When i got my 2015 car 2 years ago i had this buzz every time i switched the car off,i managed to find that it was coming from the bottom of the engine on the belt side,i found online somewhere it was because the air con needed recharged,had that done and not heard it since,i still occasionally get a buzz when switching off but this is around the top of the engine so probably ECU's.Itis nothing to do with your aircon, the ECU's buzz like mad for about 2 minutes after engine off, my Stelvio does the same thing, had it on the Giulietta and the Giulia!
Hi,no leaks,just needed a recharge,probably the first time it had been recharged,i must admit when i read that's what the problem could be i was a bit sceptical that it would work but it did for me and the buzzing before hand was easily found to be at the bottom of engine.Okay so if your aircon needed recharging did anyone fix any leaks or seals or did they just add more refrigerant?
There is a good video here High pitched buzzing after turning off carNow that is a possibility pressure equalisation once the compressor has stopped, more refrigerant would reduce the time taken for this to happen !!?
Thinking about it now and seeing that video it did sound like an alarm compared to the ECU buzz.Good to see that, this isn't the noise I know the ecu's make!
You just wonder why it is not in the manual somewhere when it appears to be an alarm type sound,probably because the dealers would lose a fortune ripping people off.The ECU's sound like a really mad bumble bee if you have ever caught one in a fishing net!!!