Thanks everyone for the great suggestions. I'll try them out and see what I come up with.
Unfortunately I can't hear the fan at all, leading me to believe that dr_spock's fuse suggestion is probably the right path. However, the fan 'turn on time' has been slowly increasing over the past 1 year. Started at a tolerable 10 minutes, then 1 hour, and now never.
I brought the car into my Mazda dealer to see what they suggest, that they said they didn't know exactly what the problem is, but it might be the thermostat. This seems a bit weird since the fan never comes on, regardless of temperature.
Heading for my fuse box, but any more suggestions welcome.
Thanks!
Mark