My Beckett furnace has been running past the thermostat setting. The other night it was 79 degrees, we have it set at 64! Yesterday I went to the store to buy a Primary Control and installed it, and the furnace still keeps running. Ive even checked the thermostat (of course) and we are totally at our wits end... does anyone have any suggestions?

Dave13

If you disconnect the thermostat wires from the primary does the burner continue to run? If it does the primary/transformer/burner motor wires are hooked up wrong.

No, I replaced the primary control yesterday and when you remove one of the wires it will shut off. I tried to remove one of the wires from the thermostat and it continues to run.

Then you have a wiring problem. Get the paperwork for the primary you replaced and wire like it says.

Could it be the limit swtich?

If you remove the thermostat wires from the primary and the burner does not shut down then the primary is not controlling the burner and associated parts. The prinary relay contacts are burnt together from being hooked up wrong or it is not wired correctly like I said before.

Disconnect the thermostat wires from the furnace primary control if hooked up there a then see if it shuts off. If not the wiring for the primary is wrong allowing the voltage to pass to the burner with out thermostat control OR the new primary contacts are burnt.