Google nest—old thermostat no white wire, just jumper

[Tmoon]

trying to install Google nest but my current thermostat doesn’t seem to have a white wire. There is just a white jumper from Y to W. How do I configure in Nest?

thank you!

https://imgur.com/QIhJgIO

[CoolingWizard]

@Tmoon , that is a very confusing since the Y wire is for a cooling, and the W wire is for Heating.  So I have to ask myself why would the HVAC technician would wire it that way. This would activate the HVAC system the same way in either heating or air conditioning mode.  You need to go to the HVAC forced air handler and see what the wire is attached to on the other end.  Can you post a picture of your current thermostat showing the wires attached to it. 

AC Cooling Wizard

[Tmoon]

Thanks for the reply! I had a link to the pic in the post. Let me know if you can see it. Just asked a neighbor who installed Nest and he said he just didn’t attach anything to the W and it works fine…. 

[CoolingWizard]

@Tmoonthe picture did not show me the terminal letters each wire is attached to. Do you have a Heat Pump system? If so you had an old thermostat that was not fully Heat Pump smart.  That is why they wired W to Y to ensure the compressor always running. Is the Blue wire attached to a terminal labeled B or O? And, is there a C terminal on your old thermostat?

AC Cooling Wizard

[Tmoon]

Blue wire attached to O.

Tbh, not sure about heat pump; not knowledgeable at all about these thing. It’s a in-unit HVAC in a 10 yr old condo. Perhaps in over my head. But thanks for your help.