e74 error at installation

[jackgoss]

I am trying to install a nest thermostat. 

I believe my system is compatible. I do have two wires connected by wire nuts, but they are not thick or stranded. 

This is a simple newer furnace with no ac.  Should be easy - only three wires: R, G, W.  But I have an e74 error saying there is no power to the Rh wire. I have confirmed with a multimeter that there is 25 v difference between the R and G wires. 

I have tried charging the thermostat via USB and it has restarted itself a couple times.  

[Patrick_Caezza]

Post a picture of the original thermostat's wiring.

[jackgoss]

[jackgoss]

Existing thermostat photo above.  I should mention that the heat does work with the existing thermostat. 

[Patrick_Caezza]

Interesting wiring.

It looks like the blue and white wires are wire-nutted together for some reason.

Can you post a picture of the terminal block on the control board in the furnace/air handler?

[jackgoss]

Thank you for taking and interest and helping. There are three pictures below.  First, the one I think is the terminal block you are asking for. the other two show that following the thermostat wires is not as strait forward as I might hope. 

terminal blockI believe this is where the thermostat wires enter the unit.some wires from the thermostat go into this plastic thing instead of the terminal block

[Patrick_Caezza]

Is there something like this installed at the thermostat?

Does you system have cooling as well as heating? or just heat?

[jackgoss]

I don;'t see anything like that.  it's heat only.

[Jeff]

Hi jackgoss,

Sorry for the delay in a response here, but I wanted to check in and see if you were able to get this sorted out or to see if you were still working on things. If you're still having issues, let me know so I can help you out from where you've left off.

Thanks,

Jeff

[jackgoss]

I have not made any progress. I would welcome any help. I looked up the add-a-wire thing and found instructions for installing it but haven't understood how to adapt to it being there.

[MelbaDT]

Hey jackgross, 

I understand where you're coming from. Are you pertaining to the Nest Power Connector? If yes and you've already installed it, are you getting a message or a code on your thermostat display? I also suggest that you try the troubleshooting guide here: https://bit.ly/3ujTiLa

Keep us posted. 

Best, 

Melba

[Ryan_G]

Hey everyone,

I'd like to jump in here and check if you've seen Melba's response. Let us know if you need more help by replying to this thread.

Thank you for your help, Melba.

Regards,

Ryan 

[jackgoss]

I'm afraid I don't understand Melba's response.  

[jackgoss]

After reading some more about the Add a Wire I went looking for something like this.  I think there is something like this attached the to the blue wire shoved into the wall where the wires come out, but I was afraid to pull on it too hard to verify.

[MelbaDT]

Hey jackgoss, 

Sorry for the confusion. You've mentioned that you've added a wire after some researches so I wanted to ask if that wire was the Nest Power Connector. Also, if you're afraid to pull out the wire to verify where it is connected to, you might want to ask the assistance of an HVAC technician or a local pro.

Best, 

Melba

[jackgoss]

I didn't add the wire, I found it like this, presumably from the last thermostat installation. I will probably have to hire someone for this. 

[MelbaDT]

Hey there,

Got it and I understand. Hiring a professional is the best option as they will need to check on that spare wire if it can be used as a Common Wire. Please contact a local pro. 

Best,

Melba

[MelbaDT]

Hey there, 

Checking back in should you still have further questions here. Let me know by replying to this thread. 

Best, 

Melba

[MelbaDT]

Hi, 

We haven't heard from you in a while so we'll be locking this thread if there is no update within the day. If you have any new issues, updates or just a discussion topic, feel free to start a new thread in the Community.

Best, 

Melba

[jackgoss]

I have not had time to come back to this project.  I will try again later when I have some free time.

[MelbaDT]

Hey there, 

Gotcha — thanks for getting back to us. I'll keep the thread open for a few more days while waiting for your update. 

Cheers, 

Melba

[MelbaDT]

Hey there, 

It' me again — how's it going now? Have you had the chance to have your system checked by a professional already?

Best, 

Melba

[MelbaDT]

Hi, 

We haven't heard from you in a while so we'll be locking this thread if there is no update within the day. If you have any new issues, updates or just a discussion topic, feel free to start a new thread in the Community.

Best, 

Melba