No power to Rh wire E74

[DB2022nest3]

Error code E74

turned the power on off, recharged nest 3rd gen thermostat, same: no power to Rh wire

solutions? It’s 53 degrees in the house 

[Houptee]

Was this working prior to this or is this a new installation of the Nest?

How many wires are connected to the base and post pics.

What kind of heating system do you have? Forced air with ducts gas? Oil, Boiler with radiators/baseboard?

[DB2022nest3]

• New installation as of October 11, 2022. Worked OK till Friday when temperature dropped to 6 outside 
• Heating is forced air with gas furnace 
• 5 wires in the base Y1, G, W1, C and Rh
• checked all, they look good 

[DB2022nest3]

 

[Houptee]

Check the Power info using the Nest on the base.

Tell us what the readings show for each.

This video explains how to do the test for the Nest Learning.

If the Vin is below 24v you might have a issue with the transformer in the system or blown fuse on the board in the system (they usually look like plug in car fuses). Or a loose R wire on the furnace.

https://www.youtube.com/watch?v=GHkfnRp6Tj8&ab_channel=OneHourSmartHome

[DB2022nest3]

vin is 0.02V

will check the rest.

Thanks!

[EdwardT]

Hi folks,

@Houptee, thanks for the help!

@DB2022nest3, how's it going with your Nest Thermostat? Were you able to check the rest of the things that Houptee suggests? Let us know if you have questions and we'd be glad to assist you.

Thanks,

Edward

[DB2022nest3]

It was the frozen humidifier pipe (that was draining outside) that prevented the furnace from starting. The pipe was replaced with another one draining in the sump pump well in the basement 

[EdwardT]

Hi DB2022nest3,

Thanks for the update. To clarify, is it working fine after replacing the pipe? Keeps us posted.

Thanks,

Edward

[DB2022nest3]

Yes, it is.

[EdwardT]

Hi DB2022nest3,

Thanks for the update! I will be locking this thread in 24 hours. Please feel free to create a new thread should you have some more questions or concerns in the near future and we'll be more than glad to help.

Thanks,

Edward