We just moved into a new house and I want to replace the thermostat. I am trying to figure out if my current setup has a C Wire.

If it doesn't, then I'll need to get a new wire run -- which I want to avoid.

If it helps, this is a White Rodgers 1F80-361 thermostat.

enter image description here

  • it does not need C wire, it is battery operated,
    – knowitall
    Jun 22 at 19:43
  • I know it is. But I am replacing the thermostat and the one I am getting needs a C Wire. Jun 23 at 2:55
  • so that is the old thermostat ? it does not have the C connected to it.
    – knowitall
    Jun 23 at 3:16
  • I guess not? I'm not exactly sure. Jun 23 at 14:33

2 Answers 2


Look at your furnace/HVAC unit's control board and see if there is a "C" terminal. If so, then see which wire, if any, it's connected to. That is your "C" wire at the thermostat.

If no "C" terminal that you will not have a "C" wire and could possibly hook one up if you have the wiring diagram for the furnace.


Assuming you show the new thermostat not the old one.

That one doe not need C- wire. It is battery operated.

It also does not have the C-wire connected in that photo.

Sometimes you get lucky and the C wire is there, just not used (probably black or blue wire.


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