airspeed indicator and VSI stops working mid flight without any failure event

[lei]

as title said, the speed indicater and VSI suddenly stops working during the flight, no failure event.

I did run out of fuel on the outer tank during the flight an i switched to inner tank right away but i am not sure if the speed indicator stopped working then. 

[Terry Dactil]

Pitot heat not on?

[grafspee]

If i cruise at high alt for long time i get this pitot failure very often only descending to low alt fixes problem.