I noticed today when I was driving my temp gauge dropped down to zero. After a little while, it jumped back to normal operating temp. Anyone know what could be the problem? TIA.

how do I "unstick" it? Sorry for the noob question.

it was already replaced a few months ago.

I had that replaced on my S4. Audi has an updated part, I believe it's pretty cheap, for the sensor an an o-ring, and it's easy to replace for DIYers. VAG the car and it'll tell you exactly what's wrong.

I don't think a t-stat can stick all of a sudden, it's failure is more gradual.