Connecting Common Wire to HVAC with No Control Board : r/Nest

Need common wire from control board to thermostat : r/hvacadvice

I found an unused wire behind my thermostat and at my control board. Is this an unused C wire that I can connect and use for my Nest? : r/Nest

How many wires can be connected to the C terminal at the furnace

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Thermostat Wires no Common Wire? Run new or Adapter? : r/hvacadvice

Nest thermostat with no power to C wire. It's connected to B/C terminal on furnace. Any advice? : r/hvacadvice

Wiring issue - no control board at Furnace for C-wire adapter