Since S2ki helped me to diagnose a tired tct which I am forever thankful for, I'm hoping someone on here will have heard this noise and have some idea what's causing it.

https://youtu.be/KbUveAbEl34

I have taken it to a garage and they changed the aux belt but that didn't stop it.

Edits:
The noise doesn't happen until a few seconds after engine switch on, I'll try and get a video example
The noise doesn't change by switching AC on and off
The noise isn't affected by engine revs, it stays the same

 

It something driven by that aux belt... I had a similar sound and it was my AC compressor. The general advice is to take a screwdriver and put it against each component and put the that you hold up against your ear, as if it is a stethoscope. You may even just be able to touch the component with your hand and feel a difference in the vibration as the noise goes on and off.

 

Oh, one thing that might help to pin point the noise. When I start the engine the noise isn't there until there's a click and a quiet high pitch "whee". Whats belt driven that takes a few seconds to kick in?

 

Does it turn off after a while of idling?

 

no, once it starts its there to stay. Even after long journeys.

 

I agree with Soviet, the clicking noise you refer to is most likely the AC clutch kicking in, try with the AC turned off and se if it still does it.

 

I'm a Brit so the AC gets used for about one week every year, and this is definitely not the week. I did try turning the AC on and off though but the noise was unaffected. With some help from someone sticking their head in the hood we've discovered the noise doesn't change with revs so that rules out bearings?

 

Is it more of a mechanical sound or could it be some kind of electrical noise/sparks from inside the generator?
I watched the video but thought it would be easier to notice the difference in real world.

 

It could be either. It's such an inconsistent sound that I thought it had to be electrical but in person it could be either. The sound in the video is really accurate.