Sundance running with ICE on display

[KMN]

There was an older post concerning a Sundance model 850 spa running and showing ICE even though the water temp was 102.  I replaced the temp sensor (in the filter compartment) a while back based on other error codes and everything has been working for a while.  It seems the last couple of times it got cold out (20 deg F) I am having the ICE problem where the hot tub thinks there is a freezing condition when there is not and runs continuously.  I have reset the breaker which did not work.  My question is if it is a sensor problem what sensor is responsible for thinking there is an ICE condition? Is it the temp sensor (that I replaced) or the other sensor in the heater or somewhere else? 

[ciderjack]

The sensor in the heater can throw the ICE code.  If your circulation pump is not set to run 24 hours, sometimes the water in the heater can get down below 55 degrees and throw the ICE code.  This is all normal.  

[RDspaguy]

Your circ pump should not turn off, but the high limit sensor can become dislodged in it's mount and read ambient air instead of water. Check the high limit sensor, make sure it is all the way in and plug the hole behind it. 

The temp sensor is exposed on the back. Sometimes it is open, others there is a tube off the back, but either way cold air can reach it and cause errors. Insulate the back or plug the tube.

Check that all sensor wires are tight in the plug and the plug is tight on the board with no corrosion on the pins. Check wires for damage.

Make sure all side panels are on and tight with no missing or broken slats. 

Sensors can be tested with an ohm meter set for 20k ohms. I recommend replacing both at the same time if there is a discrepancy.