The fan resistor is a known cause of problems and is easy to replace or fix. It is located on the passenger side behind the glovebox mounted into the airbox with two screws. Nissan is very proud of this part and the $100 plus pricetag shows this.
But, you can fix it yourself for around $10.00
This is the little guy you need to fix
This is what you need to buy, I suggest Mouser

Plus soldering iron, solder and thermal paste.
This is what is under the plastic cover
There are 5 total solder joints that need to be removed, hence the solder wick. Touch them all with a soldering iron and pull solder with wick to free connection. After this is done, circuit board pulls out and you are left with the three prong transistor and the thermal cutoff.
Remove the small screw inside to free the transistor and retainer. Apply paste to surface and reinstall new parts. The cutoff is held under the black retainer. Slip circuit board down over the new terminal ends and solder in place, trim excess connections and put plastic cover back on. Reinstall unit and enjoy your fan at all speeds
