I had a nest learning thermostat Gen3 installed a few months ago. I have an all electric heat pump system and have had no issues with cooling. Now that the weather is getting colder the heat pump has been functioning ok, but when the outdoor temperatures get really cold the thermostat shows "Alt. Stage 2", but no heat is being produced. I have chatted with support, they asked me to switch my "W1 & W2" wires, but still no luck. I have attached a photograph of the old thermostat wiring, and also the initial wiring of my nest thermostat. Am I wired up correctly for the Aux heat to kick in?
Ok your Aux is not recognized. Looking closer at your pictures, although the wiring seems correct, the tabs for W1, W2aux and C do not seem pressed, which would mean the wires are not properly inserted in the wire base. Can you please ensure they are properly inserted? See how pressed down the tabs are for the other wires, it needs to be like that.
And once you have inserted those wires correctly, go to settings->equipment-> wiring on your Nest app and make sure that it does recognize all the physical wires you have on your wire base. This will ensure your Aux is properly configured. Then you should be able to see the heat pump balance setting, suggest you start with a max savings, and work your way up if that’s not enough Aux.
Hey laurentbourg, Thanks so much for your help! After doing some digging, and downloading the nest pro installation book (something I wish my nest pro would have done...) I figured out my issue. I have a single fuel system, but the thermostat would only allow setup for a dual-fuel because there were wires in both the W1 & W2 terminals. Since my system is singularly electric, I was supposed to have the W2 (white) wire in the "W2/Aux" terminal, and the W/E (brown) wire in the "*" terminal, set to emergency heat. When I switched those wires and reset the system everything started working correctly. The reason the house was getting so cold is because when the outside temperature dropped below 30, the thermostat was cutting off the heat pump and activating a gas furnace that I didn't have, so I had no heat source. Again, I appreciate your help!!