Buzzing Dashboard Prius Gen 4

[Harters]

I have a March 2017 Prius Excel which has a buzz coming from the left side of the dashboard which started off as very light, but has now developed more and depending on temperature sounds as though something could be loose.  I only ever get it when I first drive the car after it has been sitting overnight or all day whilst parked at work.

I know in the US there was a TSB for a buzzing dashboard on earlier 2016 models and that was cured by a modification to the heater trunking in the footwells.  People were either getting Toyota to fit a modified part or were fixing it themselves by jamming a cloth up around the trunking and stopping it that way.  I have tried this on mine and I know it isn't that as the sound is coming from higher up, although I know sound does travel.

I took off the passenger side dash access panel to enable me to remove the passenger air vent as I thought it was that, but that didn't stop it.  Interestingly when the vent is removed and the noise is there I can make it worse by putting my hand in the air vent hole and pulling towards the centre of the car so its definitely around that area.  I have been a passenger and pressed varies parts of the dash, but couldn't make it go away.

The noise isn't there all the time, just for the first mile or two then it goes quiet, so I don't know if when something heats up it stops or whether something is loose and it just jiggles into another position where it doesn't buzz.  Its the same with the air con/heater on or off.

Anyone else got this?

[kithmo]

I don't know how difficult this may be to do, but have you tried taking the vent tube off to make sure nothing is inside it ?

[Harters]

10 minutes ago, kithmo said:

I don't know how difficult this may be to do, but have you tried taking the vent tube off to make sure nothing is inside it ?

I don't think it is the vent tube as I have messed with it as a passenger from underneath and through the hole when I had the vent removed and I couldn't make it stop.  Lovely smooth roads and it doesn't do it, but as soon as its a coubik textured road then it starts.  There is a flimsy piece of plastic underneath that covers the vent tubes and I have packed that as it was a bit loose and flappy thought it could be that, but no joy.

If it gets to the stage where it does it all the time I will take it in, but I know sod's law I will take it in and it won't do it  

I am coping with it at the moment as I know it goes away after a time, but if its there all the time I will definitely have to sort it.  Usually any rattle/squeaks drive me nuts, but I love this car so much I can forgive it