One w and y wire: Heating issues Nest thermostat furnace not turning on

[ums05]

1. My current thermostat wiring has one common wire for Y and W. Everything works normally with the old Honeywell thermostat. 

2. When I installed Nest thermostat, i put the common wire in Y 

3. Since then i am having issues with heating. The cooling works great, but if i switch to heating the thermostat gives issues. Sometimes it just runs the fans, failing to start the heat. Sometimes the heat starts but refuses to stop. 

Any solution here? TIA 

[Patrick_Caezza]

@ums05 

Can you post a picture of the original thermostat's wiring here?

[ums05]

@Patrick_Caezza I have attached the pic. 

Currently, the white wire goes into both W and Y through a splitter. Green goes into G. Blue goes into C. And red goes into R

[Patrick_Caezza]

@ums05 

You need to look at the control board in the furnace/air handler and see how the thermostat is wired there.

As it is currently wired, it is not compatible with any Nest thermostat.

[ums05]

Should I put the control board picture here? 

When I installed the nest it was working properly for cooling, when I put the common wire in Y. The heating was giving issues. 

@Patrick_Caezza 

[Patrick_Caezza]

@ums05 

Yes, upload the control board picture. I need to see the terminal block labels and what wires are connected to which terminal