At spring when we had ~10 degrees max outside, I couldn't get the fan working even when hard riding in forest.
Mine starts now with 20 degrees when I ride in forest and then let it idle couple of minutes. Sometimes you just don't notice it.

To check if fan is working, unplug it and use power straight from battery.

But to check if power comes to the fan: theres fuses and relays between that only give power to fan when temperature is too high. Thats read by temperature sensor.

I know that with my car I could start the fan when I jump wired two pins from temperature sensor plug. It should work the same way with XT. For my car there were 3 pins: Fast fan(very high temp), slow fan and ground.

If I remember correct, then XT engine temperature sensor had 2 pins? Then it should be easy: just use some metal to connect those pins and fan should start in theory. You should first check those pins with multimeter just in case that both are not positive wires.

Can't test it by myself right now. Hope it helps.