273 Overheating
"Ok, maybe it's circulating too fast without the T-stat and doesn't have a chance to cool down. Put a new (tested in a pan on the stove) T-Stat in, functioning, still overheats."
Untrue but often repeated because people experience overheating after removal.
Read all of these:
https://stewartcomponents.com/index.php?route=information/information&information_id=6
Dispels many myths and provides lots of useful information.