topic Re: E80, E79 error codes in Nest Thermostats

E80, E79 error codes

Lconolly — Sun, 11 Dec 2022 14:27:34 GMT

Just got our thermostat yesterday and sunk several hours into trying to figure out the correct wiring. Here’s a pic from our old one. First we got the E79 error. I feel like we tried every combination possible and received just about every E code. We have central AC and oil for heating through baseboard. Wondering if it’s just the wiring or is my heating system incompatible?

Re: E80, E79 error codes

Markjosephp — Thu, 15 Dec 2022 16:21:33 GMT

Hello Lconolly,

Thanks for posting your thermostat's wiring diagram. I'd love to know more about why it's giving you an E79 report.

It appears that your system is not providing enough or any power to the thermostat or a specific wire (as a result, the thermostat cannot complete a circuit and displays the report). To isolate, could you tell us the power readouts under the technical info option? Also, have you tried the steps in this guide?

Please let us know how it goes.

Regards,

Mark

Re: E80, E79 error codes

Lconolly — Fri, 16 Dec 2022 19:35:34 GMT

Battery

3.684 V

Voc

0.05 V

Vin

0.05 V

Re: E80, E79 error codes

Markjosephp — Sun, 18 Dec 2022 18:19:39 GMT

Hi there,

Thanks for getting the power readouts on your thermostat. It appears that your thermostat is not getting any power at all.

I'd love to know more about this. Could you share a photo of your Nest Thermostat's wiring? Also, try removing the C wire and leaving it disconnected. Note: make sure to turn off your HVAC system at the breaker box before touching the wires.

Let us know how it goes.

Regards,

Mark

Re: E80, E79 error codes

Markjosephp — Wed, 21 Dec 2022 19:35:57 GMT

Hi Lconolly,

I wanted to see if you still needed help. Please let us know if you have any other questions or concerns.

Thanks,
Mark

Re: E80, E79 error codes

Markjosephp — Thu, 22 Dec 2022 20:40:33 GMT

Hello Lconolly,

I'm checking in to make sure that you've seen my response. If you have any further questions or concerns, please let us know before we lock this thread in 24 hours.

Thanks,

Mark