Fan stopped working?

[DynaMight]

Hi guys

Any idea on this one? So I have a Hobbywing 2.1 120A, I've had it since January and its been running perfectly. About a month ago, I noticed the fan stopped working after a heat. I bought a new fan, but that also stopped working after a few heats.

I contacted the seller and they replaced it for a brand new ESC, got that today, soldered it all up and the fan stopped working after a few runs! the actual ESC runs perfectly, no glitches or anything.

The fan points are getting voltage, basically the same voltage as the batteries (I assume thats correct?) but I cant understand why its stopped. The receiver is the same as I've had for years, the only thing I've changed is I recently went from a 6.5t HPI motor to a 8.5t Vampire motor. The motor isnt run hard, its got zero boost and 10degrees turbo. Could a motor run perfectly but cause a fan to stop ?

Any thoughts or suggestions?

Thanks