I bought a new thermostat, and I need a C connector, but its missing on the unit. There is no C what so ever, but I do have a B and O connector, maybe I can use one of them for the C.

Please see the attached schematic from my machine and a pic of the connector/wiring itself.

enter image description here enter image description here


It's all in a name

The silly folks who made your air handler decided to call their C terminal a B terminal instead, perhaps because it has a blue wire hooked up to it in the wiring diagram. This blue wire goes to CN-1, which connects to the blue wire (return) from the fan relay and to the blue/black return wire to the transformer.

So, hook your thermostat C wire up to the B terminal and call it a day.

  • thanks for your quick response, so the white wire connected to the B on the AC unit has inside a Blue wire? ill check that later. so to be clear on my next step, ill take the green wire on the AC unit and connect it to the B, (leaving the existing wire connected to the B), and the green wire on Thermostat will be connected on the C connector on thermostat, and i will also get a jumper between the Y and G on thermostat for the fan. please correct if im wrong. i really appreciate the help Thanks loads. – sol jacobs Dec 14 '16 at 15:21
  • @soljacobs -- that is correct – ThreePhaseEel Dec 14 '16 at 23:11

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.