E74 code no power to rh wire.

Steveoarroyo
Community Member

Just installed a new nest gen 3 learning thermostat on 01/14/2022 which went without a hitch and worked fine until this morning. My house was cold and my nest thermostat did not show any temperature. It had a e74 code, no power to RH wire. Reset my  power and it came on for a short but it failed just minutes later. Tried again and it did not work at all with the same code. It should not be doing this and I have seen other postings with this issue. I had to install old thermostat to get my heater to work. There is no reason or excuse why this thermostat which is not cheap should present these issues. Would like to know if there is a solution for this problem since I am not the only one experiencing this problem.

6 REPLIES 6

MelbaDT
Community Specialist
Community Specialist

Hey Steveoarroyo, 

 

Sorry to hear about your experience but thanks for posting. 

 

Just to confirm, when you tried connecting back your Nest thermostat, did you ensure that the wires are properly seated? If unsure, could you make sure of the following:

  • Check that each wire is fully inserted into its connector and that every connector with a wire is down as shown.
  • Check that each wire has ⅜ inch (6mm) of exposed wire.
  • Turn the power to your system back on and check to see if your thermostat is working.
  • Check that each wire is connected properly to the system board.

I also suggest that you check on this link for more troubleshooting suggestions. 

 

Best,

Melba

 

I am having the same issue with the RH wire. I am getting an E74 code. Please help

MelbaDT
Community Specialist
Community Specialist

Hey there, 

 

Just checking back in — do you still need help with your Nest thermostat?

 

Best, 

Melba

MelbaDT
Community Specialist
Community Specialist

Hi, 

 

Since it's been since this thread was last updated, we'll be locking it if we won't hear back from you again within a day. Should that happen, feel free to create a new one should you have more questions or have other concerns in the future. 

 

Thanks, 

Melba

M18nest
Community Member

My Nest was installed in September and worked fine in AC mode through January. It worked in Heat mode until today (February 18) when I returned it to AC. It was working when I left home. Upon returning it was offline. The thermostat had an E74 code. I checked the circuit box and reset the breakers. Nothing changed. The Rh connection appears good. What is happening? Do I have to reinstall the old thermostat? 

Same thing happened to me.  And my thermostat is less than two years old.   Technician came out and verified that the thermostat was defective and was not relaying to my unit properly.  

The technician verified all of the wiring and that it was wired correctly but Thermostat was not sending of Romero on to relay and said I would need a new unit.

if Google does honor an exchange for a less than two year old thermostat, I will be switching brands.  Already phasing out Google products because of issues such as these.  As for thermostats, EcoBee and Honeywell seem to have good overall track records and back their items better.  So if you change , I would look to those companies.  Especially, Honeywell.