If you're thermostat wire are ONLY 4 wires. Take the Green wire behind the thermostat and put it onto the C terminal, and do the same thing to the furnace control board, take the Green wire off the G terminal and put it onto the C terminal
Typical thermostat wires used are Red to R. White to W. Green to G. Yellow to Y. The Blue wire goes to C terminal on both, thermostat and furnace control board
Mike, C wire isnt required. The C wire is where it keep the battery charged. Aside from that you'll have to charge it every year or so. Which only take about 15 minutes
