Aux / pusher fan dead

[X5Kiwi]

The last few weeks I've noticed that my aircon was not particularly cold driving around town, and only really got working at open road speeds, but even then never really cooling down to the nice 18C that I like.

Today I finally figured out that my aux fan was not working, and that the 50amp! fuse (#61 in glove box) for it was blown.

Since there was a spare fuse sitting right above it, I thought I'd try my luck replacing the fuse and seeing if everything worked ok.

However the old rule that fuses only blow for a reason was true, and no sooner had I replaced the fuse and walked around to the drivers side when I noticed a huge plume of smoke coming up from under the front of the bonnet!

I ripped the fuse back out, but it had already burnt out. The smoke was coming from the aux fan area, so I assume it is stuffed?

Replacement fans seem massively expensive ($800+ locally) so my question is could it be the fan that is at fault, or could something else be faulty, and that has killed the fan (and will kill a new one?)

Also, has anyone purchased some of the non original fans from EBay like this one 00-06 BMW X5 E53 AC Radiator Cooling Auxiliary Fan Assembly Air Condenser Motor | eBay and do they work ok?

And why does such a small fan need such a huge amount of power, 50amps seems like a lot to me!