I am in the process of installing a new thermostat that requires a c wire. I checked my thermostat to see if it has a c wire running to it and it does not. After doing lots of googling and watching youtube video I think I know what to do but would like somedody that knows to verify it is correct before I attempt something like this.

I noticed where the wires run to the thermostat it has a extra wire (orange) not in use.

thermostat wiring

I then checked where the furnace to verify the same wire is not attached to nothing and it is not.

furnace wiring

If I am looking at it correctly I can connect the extra wire orange to the to the orange wire from the furnace which is not connect to anything (which if I am reading it right is the c wire) This would work correct? I am new at this and do not want to mess anything up.

  • 1
    The wires in the thermostat are stripped back way too far. Trim them down and reclamp them. – ratchet freak Jun 20 '17 at 9:36
  • Common convention is to use the blue wire for C, if it's unused. – Harper - Reinstate Monica Jun 20 '17 at 16:38

It's a little unclear exactly what you're asking, but it sounds like you're on the right track. If the orange wire is unused (unconnected at both ends), you can use it as a C wire. Connect the one end to the thermostat's C terminal. Then connect the other end to the C terminal in the furnace.

If the furnace does not have a C terminal, please see this answer for help figuring out where to connect the wire.

According to the schematic, the grey wire should be C.

enter image description here

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  • Thanks, and just to be sure based on this picture (link listed below and zoom in to see the diagram in the back) the c wire is orange correct? Thanks, flic.kr/p/VXVpiZ – Jeremy Jun 20 '17 at 15:40
  • @Jeremy Umm... No. That diagram is for the blower motor. If you look at the rest of that label, you'll likely find a wiring diagram for the low voltage control wiring (which is what you're dealing with). – Tester101 Jun 20 '17 at 15:55
  • bummer, I tried looking and I am having trouble finding a diargram but I am not sure what I am looking at so I could be overlooking it..What should I do? The model is e3eb-017h. and Is the smaller thin wires that have the wire nuts on them the thermostat wires? I noticed they are the exact same colors that are under the thermostat itself. A full pic of what I see when I open the door is below. thanks for your help, flic.kr/p/UGkHkf – Jeremy Jun 20 '17 at 16:55
  • @Jeremy on the same label as the motor wiring diagram, to the left, there's a schematic. Please post a clear photo of that. – Tester101 Jun 20 '17 at 19:55
  • thanks link to new pic is below also noticed the blue wire is not attached to anything but under the thermostat it is attached to g. flic.kr/p/UKAVra – Jeremy Jun 20 '17 at 21:50

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