Nest Thermostat is not heating

[Marcus5]

My Nest Thermostat stop working properly two days ago, out of the blue. When set in heat mode the Thermostat will not turn on. It says “in 40 minutes or 1 hour” but never comes on. The only way the heat comes on is by changing the thermostat to test mode and then the heat pump turns on.  The thermostat has done this before in Heat and Cool mode. I didn’t do anything to fix it and it resolve itself. But, this time it refuses to cut on. In an attempt to resolve this issue, I have factory reset the thermostat and reconnected it to the network. Also, I pulled the face plate off and charged it with a usb charger. I changed the air filter. I check my history and it shows that it is not on. The temperature outside is below freezing and I am in dire need of assistance. 

[RenzJ]

Hi Marcus5,

Thanks for posting here in the Google Nest Community. We're sorry for any trouble this may have caused you. Let's see what's going on. Please answer the following:

1. Are you from North America or Europe?
2. Gather Nest Thermostat power readings in Settings > Technical Info. (VOC, VIN, LIN, and Battery Level.)
3. Send us a photo of the Nest thermostat wiring and control board wiring.
4. Are there any wiring reports or alerts on the thermostat display during the time it was installed?
5. Is there a wire connected to the C terminal of the Nest thermostat base?
6. Do you have a multimeter?

I look forward to your response.

Best,

Renz