Extruder fan not spinning, bubbles and smoke

My Vertex’ centrifugal fan suddenly stopped working during a print. The print was almost done, so everything seemed fine. However everytime I attempt a new print, the fan does not start and there’s smoke coming from the extruder. Also, some melted filament bubbles out between the hot piece and the connecting plastic tube. I assume that’s because of the missing cooling?!

Any ideas on how to fix this would be very much appreciated…

Good grieve, that*s a lot of stuff.

For the fan please check the small resistor on the PCB on the print head. Maybe this one is damaged and now generating the smoke. In this case the fans would barely run.
Please disconnect the large fan and check if the small fan is still working (without smoke ?!?).

So far the first attempts for the fans.

For the bubbles of filament I cannot understand where exactly it comes out, so please describe it a little bit in detail (a picture would be helpful). There are several possible reasons for that.

However, you may find my own blog helpful in this case (http://ddd.k8400.hoehnemann.net/)