We setup a sensi smart thermostat by combining the Blue and Orange wire into the O/B connector and Black to C. This had the heat and fans working but NOT cooling.

We adjusted by trying to put Blue elsewhere. Once this happened, no fans or heat or cooling.

We decided to just put the old thermostat on because its cold and now the old system isn't working.

Can we restart the old system some way?

What would have been the proper wiring to the new thermostat

Attached is the photo

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  • No "attached". Picture of the old thermostat, existing wiring and model # of new thermostat would help. – manassehkatz-Moving 2 Codidact Dec 27 '20 at 2:26
  • You probably shorted out the furnace. Check the furnace control board for a blown fuse. – DoxyLover Dec 27 '20 at 3:04
  • Can you post photos of the wiring at your old thermostat and your air handler/furnace please? I don't think whatever you tried to "attach" posted... – ThreePhaseEel Dec 27 '20 at 3:25
  • 1
    Can you post photos of the wiring at your air-handler/furnace, as well as the wiring diagram for your indoor unit, please? We'll need to know that in order to crack this... – ThreePhaseEel Dec 27 '20 at 4:10
  • the use of both O and B terminals is somewhat surprising. – Jasen Dec 27 '20 at 6:30

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