Causes
- The mist level is set to 0 (off) — the most common cause by far. The 516S defaults to a plain fan mode and will not atomize water until you raise the mist level (1-3) on the front touchscreen, the infrared remote, or in the DREO app. Owners have reported "the fan doesn't mist" right out of the box when the mist level was never turned up. As a visual clue: while misting is active, the display shows the room humidity percentage; when mist is off, it shows the fan speed instead.
- The water tank is empty, not seated properly, or the base is overfilled — the 1.3 L removable tank must be pushed down firmly so its outlet valve opens against the base. The 516S automatically stops misting when it senses low water, and it also refuses to mist if the base itself holds too much water (the tank, not the base, is the intended water reservoir). If you poured water directly into the base instead of the tank, the mist function may not start.
- Auto Mode has already reached your target humidity — in Auto Mode the built-in temperature/humidity sensor shuts the mist off once the room hits your chosen humidity target and only restarts it when humidity drops. The RGB light ring turns red when humidity is too high. The fan keeps running, but mist stays off — which looks exactly like a broken mister.
- Mineral scale has built up on the 1.7 MHz ultrasonic plate — hard tap water leaves white calcium deposits (you'll see "white dust" floating in the tank) on the ultrasonic atomizing plate. A scaled plate can't vibrate the water into 11 μm droplets, so mist output drops to nothing even with a full tank and the mist level maxed out.
- The mist nozzle or air inlet is blocked, or detergent residue remains after cleaning — the mist nozzle at the front of the unit can clog with dust or scale, and a blocked rear air inlet stops the airflow that carries the mist. If you cleaned the tank or base with detergent and didn't rinse thoroughly, the residue coats the ultrasonic plate and kills mist output.
How to Fix
- Turn the mist level up and confirm it on the display — press the mist control on the touchscreen (or remote/app) until the mist level is at 1 or higher — don't leave it on 0. The display should switch from showing fan speed to showing the humidity percentage, which confirms mist mode is armed. If you see humidity on the display and still no mist, continue below.
- Run it on the highest mist setting for a few minutes — set mist level to 3 and let the unit run for 3-5 minutes. Fresh ultrasonic misters sometimes need a moment to start atomizing. Once mist is visibly flowing, dial the level back to your preferred setting. This is the first thing DREO's own 516S troubleshooting list recommends.
- Check the tank, base water level, and seating — remove the 1.3 L tank, fill it (purified or distilled water is best), and reseat it firmly until it clicks down against the base so the outlet valve opens. If water has pooled in the base, empty the base and refill only the tank — the 516S stops misting when the base has too much water. Make sure the unit sits on a flat, level surface, since a tilted base also confuses the water sensing.
- Exit Auto Mode or lower the humidity target — if the fan runs but the mist stays off, check whether the fan is in Auto Mode. Switch to a manual mist level, or lower the target humidity in the app so the mist is allowed to run. If the RGB ring is red, the room humidity is above the safe threshold and the unit is deliberately refusing to mist — ventilate the room and retry.
- Descale the ultrasonic plate and clear the nozzle — unplug the unit, empty the tank, and clean the 1.7 MHz ultrasonic plate in the base with a soft brush and a little white vinegar or citric-acid descaling solution (never scrape it with metal). Rinse thoroughly with clean water. Clear the mist nozzle at the front with a soft brush or cotton swab, and check that the rear air inlet is unobstructed. If you recently cleaned with detergent, rinse the tank and base several times to remove all residue.
- Power-cycle the unit — unplug the 516S for about 30 seconds, plug it back in, refill the tank, and retry at mist level 3. This resets the water-sensing state after a refill or a low-water auto-stop.
- Contact DREO support if mist still won't start — if the tank is full, the mist level is up, the plate is clean, and the unit still won't mist, the ultrasonic plate or its driver board may be faulty. Contact DREO support (support.dreo.com) with your order number — owners of the TurboCool line who hit a true no-mist defect were sent replacement units under warranty.