Does the value ever change, or is it always exactly -36.0 ?
I don't know the details of these circuits but years ago I did work on a big PowerFlex 700 whose heatsink sensor was disconnected, and it gave a fixed negative number. It's been a long time (and I no longer work for that employer) so I don't recall the details.
In general if it's an RTD, then you have a damaged feedback circuit. If it's a thermocouple, it's wired backwards.