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Thread: Is this the same wire?

  1. #1
    Junior Member

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    Question Is this the same wire?

    I'm trying to figure out if I have a C wire or not. When I took the thermostat off of the wall, there is an extra wire that is blue. It's not plugged into the C terminal. The old thermostat had a battery backup, so a C wire wasn't needed.

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    However, when I looked at the furnace, there is a wire plugged into the C wire terminal that is white. There are no loose blue wires in the furnace, and no extra white wires at the thermostat.

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    Is it possible that the white wire plugged into C in the furnace is the same wire as the blue wire that is not plugged in at the thermostat? Maybe they were spliced somewhere that I can't see?

  2. #2
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    The white wire that is connect to the C terminal is most likely from the outdoor condensing unit. The blue wire that you are looking for may be wrapped around thermostat cable at the furnace.


  3. #3
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    Quote Originally Posted by Thermostat View Post
    The white wire that is connect to the C terminal is most likely from the outdoor condensing unit. The blue wire that you are looking for may be wrapped around thermostat cable at the furnace.
    Thanks for writing me back. I looked, but I didn't see any wrapped wires. I saw two other blue wires that were plugged into the circuit board, though, so maybe it was one of those that were no longer needed?

    I bought a Nest Learning Thermostat, I believe it doesn't need the C, but I'm worried about it power stealing. What should I do?

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