I have a sunbeam ultrasonic humidifier that stops misting an shows as empty when is still half full

I've never seen this model, but it would suggest that the unit is unable to function due to either an electrical failure or needs a serious deep cleaning (esp.the part that interacts with the water to form mist.) I would completely empty the unit and clean it, then partly fill the reservoir with 50/50 mix of white vinegar and water and let it sit for 24 hours (possibly longer) to remove any deposits. (Doesn't take much build up to kill the ultrasonic process). Other than that, try calling the manufacturer and see what they will do for you. (Think it's Sunbeam).

I have had times where my Crane humidifier won't produce mist if I haven't turned it on for several days (4+) or more. The water that sits in the reservoir may develop a film on the ultrasonic element which inhibits the creation of the mist to come out the top of your humidifier. I would lift off the tank and empty the reservoir. Then VERY GENTLY with a piece of paper towel, wipe the ultrasonic element (looks like a disk the size of a quarter at the bottom of the reservoir) to clean off any film. Then replace the tank and let the reservoir fill up the tank and try it again.

If your humidifier runs properly for a minute and then makes a whirring noise and goes silent (like the motor stopping), then it's a motor problem. The humidifier motor may have gone out of alignment due to bumping or rough handling of the humidifier when cleaning or emptying it. If that is the case, you will have to empty the humidifier reservoir, unscrew the base, and find the screws holding down the motor and check for misalignment. Loosen them a little and put it back together and try again.

Best of luck
thebqe

I am having this exact same problem, have you found a solution?

Same problem. It worked for about a week, then gradually stopped producing mist. No solution.

if it's a cool mist unit it will not produce any mist. now if it's a warm mist unit it should. that's normal. it is possible to replace the transducer if it is damage but you are going to have some leakage from it. but the only way to get the transducer mainly is from the manufacturer

It sounds very much like the transducer has failed. This is likely a crystal transducer and since they produce the agitation that should cause a mist, they are running continuously; not a good thing for something that is trying to shake iteslf apart all the time. These require input from a circuit that produces the fairly high level of power needed to drive the crystal so it could also be the source of the problem.
This isn't something an owner is able to diagnose unless they have some technical training.     

I see you have been waiting on a response for some time and I suggest you contact Sunbeam (if you haven't done it already) at their website for Canada:
Sunbeam Canada Customer Service 

Located My Manual:
Hope this helps!

1. Remove tank from base. Turn upside down and unscrew filling cap. Fill tank with clean, cool, distilled, or tap water. Water temp should NEVER be too hot or too cold. Return tank to base and let sit for a few minutes. Be sure the filling cap of the tank is tightened firmly.

2. Plug power cord into a 110-120V AC wall outlet only. Turn power switch to "on" position. Power light will illuminate. Turn mist nozzle until desired level is being released. Aim nozzle away from furniture and walls.

3. Always turn humidifier off when water runs* out. Unit will continue to operate when tank is empty.
*Humidifier will run up to 12 hrs on low; 6 hrs on high.

DO NOT LET WATER SIT IN TANK FOR LONG. THIS CAN ENCOURAGE BACTERIAL GROWTH.
Place unit on level surface away from direct sunlight.
DO NOT ADD MEDICATION OF ANY TYPE INTO THE NOZZLE, BASE, OR WATER TANK.
ALWAYS LEAVE ROOM DOOR PARTLY OPEN. DO NOT MOVE, TILT, OR EMPTY WHILE OPERATING.

Mild bleach and water solution for cleaning, never detergent.
Clean every 3rd day during use. Clean after long storage
Humidity varies from room to room. Aim for 30 - 50% relative humidity. If windows/ walls fog or frost, reduce mist intensity. If room too humid, ventilate by opening door or window; adjust mist intensity.

The Problem is minerals in the water. Impeller and ultrasonic designs send these minerals into the air. If the water in your area contains a lot of minerals, you will notice them as dust. The EPA does not issue health warnings about minerals in the air, but does recommend using low-mineral water (such as distilled water) in your humidifier. Many ultrasonic models feature a demineralization cartridge that filters minerals out of the water to prevent the dust.

Good Luck.