Sometimes when I turn my RX on, I get an immediate buzzing sound from what sounds like behind the radio/navigation area. Seems like now that the weather is turning cooler in the Northeast, this is happening more frequently in the morning. It stays on for however long I have the power on in the car, but stops as soon as the power goes off in the car. The battery was replaced only last year by a Lexus Dealer. Not sure what is going on? Doesn't happen all the time, but seems to be happening more often now. Just a very annoying buzz sound that almost sounds like if I hit the radio with my hand, it would stop. Anybody know what's going on here?

 

I believe it is a cooling fan for the Audio/Navigation system similar to the desktop at home!
I also was curious about that buzzing sound. You can try what I did: click twice on the engine start push button without touching the pedal to bring the gage lights on without starting the engine. This will fully power up the system without the engine noise being present and report back.

Thanks, h