I have an older furnace, on the switch block I have Y,C.W,R and an unlabeled screw that connects to the shut off it looks like. I need to hook up a thermostat that needs the C wire. I have a spare wire, in the bundle which I hooked up to the c terminal downstairs, from these videos that I've seen it tells me to then bridge the Y and G together, I do not have a G on the block, what do I need to do to get the neutral wire set up

  • Forgot to add that I have gas heat only Mar 7, 2013 at 17:07
  • What is the make and model of the furnace?
    – Tester101
    Mar 7, 2013 at 17:27
  • After more testing I discovered even though its a c wire, it's not pulling 24v, so I'll need to add another 24v to the one wire Mar 7, 2013 at 17:32
  • It's only a C wire, if it's attached to the C terminals at both ends. It sounds like you're not sure what you're doing, you might want to contact a local HVAC technician before you fry your furnace.
    – Tester101
    Mar 7, 2013 at 17:37
  • 1
    This answer might be helpful.
    – Tester101
    Mar 7, 2013 at 18:26

1 Answer 1


You have a C wire, so use it - you don't have to bridge as that is only necessary if you don't have a spare wire.

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