These are copied and pasted from a Dometic AC manual. It is describing the freeze sensor when used with the CCC II thermostat. The sensor may have failed or come off where it was installed. This is a photo of a sensor used on Dometic AC's.
3) A Freeze Control Sensor connects to the Electronic
Control Box to allow for the prevention of
freezing coils. This sensor lead is inserted into the
Box and plugged into a connector for that purpose.
1) Snap the Freeze Control Sensor (Part No.
3106480.001) onto the return bend of the evaporator
coil. (See figure below).
a. Locate "D" shaped notch in the flange of the
evaporator coil.