Humming Noise In Dashboard- Changes With Acceleration

[sandiegoken]

My 99 GS 300 has a humming sound in the dash- sounds like it is in the middle area. The noise changes tone as I accelerate and seems to disappear at higher speeds. Any ideas on what is causing this and a remedy???????

[stroked4.6]

Do you have an aftermarket stereo?

[sandiegoken]

Do you have an aftermarket stereo?

No - everything is standard.

[stroked4.6]

Sounds like interference from the alternator. Maybe a diode is on its way out. So as the alternator is spun quicker with the engine revving more the noise is louder. This same thing happened to a friend of mine. The electrical signal from the alternator was making its way through the stereo into the car.