On Nov 25, 6:05*pm, (Doug Miller) wrote:

Uh-huh. Did you ever check the rating plate on the heater?

Well, no, I didn't. There's not one in an obvious location.

But do you realistically think this could be the problem?

These aren't plug in portable heaters. They are installed baseboard
heat, have been in place since the house was built c. 1960. They all
appear to be the identical make and model. I've put a meter on
several thermostats, ones that work and ones that don't. All have 240
volt power. All the thermostats are rated for 240.

Do they even make a 110 V model? I guess it's possible but I've
certainly never seen one.