How it oscillates (a chain that turns fast spin into slow sweep)
A fan's oscillation isn't a second motor — a worm gear on the motor's rear shaft drives a set of reduction gears, which drive a crank and linkage, turning thousands of RPM into one slow sweep every few seconds. Three checkpoints live on this chain: the oscillation knob (a mechanical clutch) — pushed down the gears mesh, pulled up they part; the gearbox — its grease dries into black glue that locks the gears; the linkage screw — years of vibration loosen it on its own. So when the blades spin and the head won't move, the main motor is innocent — every suspect lives on this chain.
Match the evidence
- Blades spin, head doesn't move at all → Look at the knob on top of the motor head first: pulled up = clutch disengaged — service statistics blame pure operator error for about 5% of "no oscillation" complaints. Press it down until you hear a "click" (the mesh), power on and listen for the gears, then watch a full sweep for 30 seconds. Knob down and still nothing = a rattled-loose linkage screw or a slipped gear.
- Clicks "click-click" stuck at one end of the sweep → Dried gearbox grease (about 60% of cases): a periodic clicking = gears turning but slipping. Open the gearbox cover, clean the black glue out with alcohol and cotton swabs, and refill with a pea-sized dab of white lithium grease — not WD-40 (a penetrating degreaser that dries out again in weeks), not bearing grease (a dust magnet). Reassemble snug and run on low for 5 minutes to spread the grease.
- Oscillates fine but the whole fan hums and shakes → Dust-unbalanced blades or a loose blade nut: unplug, wipe every blade clean, tighten the center nut, and check the guard for dents rubbing the blades. Uneven dust = a running weight imbalance — the shaking is the dust telling you where it lives.
One non-negotiable rule: when the head jams, never force it with your hand — one person grabbed a stuck head, heard a sickening crack, and stripped a gear tooth clean off. A jam means unplug and hunt for a tiny obstruction, a loose screw, or gummed grease — not brute force. Another line: if the blades only spin after a manual flick, the start capacitor is bulging (replace with the same µF rating, $2–5 — but capacitors hold charge; don't touch the terminals unless you know how). A burnt smell or a thermal fuse that keeps tripping is winding territory — stop using it and send it in. And never over-tighten plastic screw bosses — a stripped thread ruins the whole assembly.