Error Code N72 with Grey Display of Rh (Heat Power) caused by flipped wires at Zone Valve

[Vikram2]

I installed a New Google Nest Learning Thermostat Version-3 yesterday, and got Error Code N72, suggesting to check Battery &/or Connection to Furnace.  I could NOT find any Batteries in this Thermostat, but checking the wires of the Zone Valve connection, I found that the wires "for that Particular Zone Valve" were flipped by the Plumber who installed my Smart HTP Wall Mount High Efficiency Furnace in 2019.  So, Swapping the Thermostat Wire Connections for Rh & W1 RESOLVED the Problem.  I saw mention of this type of Problem from others during past 2 Years, and hope they will see How I was able to Resolve the Problem.  

[Markjosephp]

Hello Vikram2,

Thank you for taking the time to let us know about your inquiry.

It appears that your thermostat detects the wire mechanically but not electrically. To isolate:

1. Please gather the power readouts on the Technical Info.
2. Make sure to turn off any available power source.
3. Remove the thermostat display from its base.
4. Remove the wire in question.
5. Try to straighten, strip, and reseat the wire into its appropriate terminal on the base.
6. Place the thermostat display back at its base.
7. Turn the power source back on.
8. Please share with us a photo of your previous and current thermostat's wiring.

Let me know how it goes.

Regards,

Mark

[Markjosephp]

Hey there,

I'm checking back in. Were you able to do the steps above? I'd be glad to hear from you — I'd like to make sure everything is working.

Thanks,

Mark

[Markjosephp]

Hi Vikram2,

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

Thanks,

Mark