I just replaced a MEARS thermostat for my electric baseboard heat that would only operate in the full on or full off position. In other words "all or nothing".

I put in a new MEARS M 612 and wired it the same way the old thermostat was wired. This also agreed with the schematic that came with the new thermostat.

I'm having the same symptoms. All or nothing. Is it possible that I may have another defective thermostat?

I checked the lines at the baseboard unit and when the thermostat clicks at about 65 degrees nothing comes through to the heating unit. When I put it up to the maximum, I then have 240 watts at the baseboard unit.