One red and one white wire only

[Brad635285382]

My only thermostat was using only One Red and one white wire only to run both heat and a/c. Is this compatible for nest learning thermostat? If so, how do I wire this?

[CoolingWizard]

@Brad635285382 , 

What is the model of your thermostat.  With only two wires you cannot activate cooling versus heating. You either have a digital thermostat that uses the two wires to communicate with your equipment.  Or, you live in an apartment building and your system uses hydronic supplied by the building.  

AC Cooling Wizard