So with no warning I've got a noise for about the last 3 days or so.  The UK RH drive diesel Octy Estate 2014 has done around 100,000 miles.   

I would say it's within the cabin, coming from behind the rough area of the drivers side dashboard, possibly just to the left of the steering wheel.

The best description I can come up with is that it sounds like when an old style speedo cable used to get dry and clicky, but I can't imagine modern cars having this issue.  It is loud enough to be heard over speech and quiet music

 

It comes and goes, but it's there more often than not.  However, I fully expect if I pulled into a garage the moment I said to mechanic 'listen to this' it would stop!!!  I can stop it by turning off the aircon fan with the knob, but it doesn't change in speed if I change the fan speed, thus it appears connected to the running of the aircon system, but maybe not directly concerned with the fan itself?  If I stop at a set of traffic lights with the engine running the noise doesn't stop.  I have tried banging the dashboard in various places (trying to miss the airbags) and it doesn't change things.  The car had a full dealer big/main service including pollen filter, at the beginning of December.  I also don't have a local dealer I can easily take it too (I have to arrange services at the wrong end of a 100 mile trip I sometimes have to make).  I do have a friendly garage mechanic who might be able to help with taking things apart and who has heard said noise, but he is baffled at the moment, and mainly works on restorations of petrol cars and isn't keen on diesels anyway.  I just wondered if this sounds familiar to anyone which might point us in the right direction?  With many thanks for any thoughts.

Edited 17 February, 20251 yr by OctaviaJo

The noise is still there - as soon as I turn on the fan it appears, but is not linked to the speed of the fan - no matter how fast the fan runs the noise frequency is constant.  Also, it might be worth noting so far there are no dashboard warning lights on with it. I've just been to see if I can record it, but no it's not going to do it to order,  Though whilst stationary with the engine running if I turn the aircon fan on and off there is a vestige of the same sound that I can hear - possibly from the under main dashboard vent in the centre of the car dash, closest to the steering wheel.  Is it possible to get those vents out and see what's under them maybe? 

Well I've listened to what I recorded and the vestige of the sound is on this.  When it gets going it's louder and constant - hope this might help

I wud take the blower out and see if there is some trash. Youtube has many tutorials for octavia 3 blower motor removal, easy job.

I looked for the blower motor removal and encountered this thread https://www.briskoda.net/forums/topic/445583-replacing-heater-blower-motor/ with a description of a 'grasshopper' in the dashboard - I think it could be the same thing - I've uploaded a longer video of the sound onto that thread hoping that someone might be able to confirm the ID. I don't know if I am confident enough of being able to get the glove box back in to be contemplate removing it, but I someone can confirm the noise, I know someone that might try the job for me.