Sounds like Aquarite. Usually, it means that the thermistor is bad and the cell needs to be replaced.
What are the first seven characters of the cell serial number?
For example, 3E13030
3 = 3 year warranty
E = Cell
13 =2013
030 = 30th day of 2013.
LCD display will read “COLD” when the water temperature is below 50 F.
LCD display will read “HOT” when the water temperature is above 140 F.
If the water temperature reads greater than 140 F, the cell temperature sensor is shorted and the cell needs to be replaced.