Def Fluid Still cool.
My purpose of installing a temporary temperature sensor and monitor at the DEF Tank was to watch for accidental failure of temperature switch that controls engine coolant to flow engine radiator fluid to pass through the heating loop inside the DEF Tank. If I understand the process correctly, the temp switch only opens when OAT(ambient) gets down close to 12 degrees(where DEF Fluid freezes). If the temp switch opens prematurely and 170 tp 210 degree radiator fluid heats up DEF fluid , it will cause ammonia gas which damages the Shaw DEF Sensors , possibly sending fault codes. If I observe high temperature from DEF Tank , I will then install a shutoff valve to keep radiator fluid away from DEF Tank. Right now ( or last 2 trips) our 2021 45 OPP seems to be working as designed as the DEF Tank is running just a few degrees above ambient. Not sure if this answers the question or not. Stay Safe.
2021 Tiffin Allegro Bus 45OPP East Central Florida