Thermostat setting tabs....

[mrcaptainbob]

What do the tabs control on a furnace thermostat? I see two would be for the turn on/turn off fan control and a third would be for the max bonnet control. But what is the last 'bump' that looks like a dollop of solder for? That is unmoveable. Not that I tried.

[Jim-Martin]

not a very good description

Just guessing.

Sounds like an old system.

Back in the day they used to put the solder on there as a heat limit control.

The solder would melt and the unit would shut down.