Older M55's did not work that way. The inserts had the two red wires connected to the Motherboard and were just hanging while the FS's had a push on connector built in on the back. I know a lot of other stoves that did have a jumper connected and even older Enviros always had the little "u" jumper on the MB. Maybe they made a change, nice that someone found it and put it out here to us for our own info...