Found it in front of the radiatior, thanks to all. Now, how do I get to it?
Can't get in from the top or the bottom. I disconnected it from the plug and
the display went to 0C. Reconnected it and it went back up to 128 so I know
I've got the right thing. That part wasn't hard, but getting my fingers and
tools through that grille to change it out just ain't going to happen!