The fan in one of our bathrooms failed.
The culprit was most likely a blown thermal fuse. Opening the motor housing to get access to the fuse was a bit tricky. The housing is held together by folded tabs as seen below. They require a bit of force to open.
Once opened, I was able to locate the fuse and cut it out.
The original fuse acted as both a thermal fuse and a current fuse (it was rated for 115°C 2A 250V). I was not able to source an exact replacement. However, I learned that I could achieve the same effect by using two fuses in series - a 115°C thermal fuse and a 2A current fuse. I was able to source a 117°C thermal fuse and a 2A 250V current fuse.
The original insulation was no longer long enough to cover the exposed connections. I was unable to source the exact insulation. Instead, I used fiberglass tape (rated for 130°C).
While I had the fan disassembled, I wiped off the accumulated dust, and lubricated the bearings (using “3-IN-ONE Multi-Purpose Oil”).
I am not sure what caused the original fuse to blow. Best case scenario, it was defective and failed prematurely.
This repair was done back in December 2018. I finally got around to creating this write up. The fan continues to work with daily use.