Norcold Thermistor Assembly 629409 Rod/ Air (fits the 2118 model) This is the current rod/ air thermistor for all 2118 models, regardless of serial number. Fits all: 2118IM 2118IMD 2118IMSS 2118IMSSD 2118IMWPM 2118IMWPMD 2118IMBK 2118IMBKD1200