Noise on Vw Bora Board

Greetings to all: I have a VW Bora (Jetta, in some countries), model 2005, which makes me a strange noise on the board, at the height of the glove compartment (lower right side). It is not a strong, but constant noise, similar to that of a drop falling. He only does it with the engine on, and although it is not so annoying, if I am intrigued where it comes from, because it may be converted into some failure.
Does anyone know what can be treated? Of course, thank you very much.

Greetings from Córdoba, Argentina

There are models that are equipped with refrigeration in the glove compartment .... Better check it! ... identify the noise well to rule out that it is an electrical component or some noise that comes from the outside of the cabin that generates some engine oscillatory accessory ...

Thanks for your prompt response; The sound (it seems to me), is similar to the one who would make a plastic gear that turns, which is missing a tooth (is understood?). In the engine it is not heard, it is clear that it is on the inside of the vehicle. He only does it with the engine running, he does not do it with the contact on. I will continue to investigate a little, to see if the glove compartment is refrigerated or not.