If you can hear it its probably fuzzed up. The grille comes off backward i.e. toward you, the rest pushes out forward so remove the ACC panel and / or adjacent switches. Vacuum the fluff out, careful of the thermocouple or whatever it is, and use a damp Q-tip to clean the vanes. The bottom cover can be un-clipped if you want to put a drop of oil on the bottom end of the shaft.
Give it 12 volts at the + and - terminals before and after cleaning, to observe the difference. Connect an ohmmeter across the other two pins and observe the reading as the temp of the thermocouple changes. 50˚F should be 18.5 to 21.1 ohms, 68 should give 11.7 to 13.1