If the dehumidifier runs continually and constantly collects water, it's likely that the dehumidifier's capacity is too low for the space; add another dehumidifier to the space to increase the water-collection capacity.
A defective humidity sensor can also cause the dehumidifier to run constantly. If the evaporator is iced up and not defrosting, you may need to replace the dehumidifier defrost sensor-, because the unit won't collect water if the evaporator is iced up.
If you see no frost on the evaporator while the dehumidifier is running, and the dehumidifier isn't collecting water, the dehumidifier may be low on refrigerant or the compressor may be defective. See the repairs below for ways to correct the problem.