Tunze USA, 305 Victor St, Austin, TX 78753, the best would be to include the power supply and pump as occasionally a fault in one of these parts can cause what seems to be a controller problem, the power is weak or the pump is dying and taking too much power to run.
As for what Allmost said, a good definitive test if it could be cleaned is to dry the sensor completely, if it looks hazy or feels rough, like dried salt, then a longer soak may fix it.