topic Re: Nest learning thermostat error code e72 in Nest Thermostats

Nest learning thermostat error code e72

lofton — Sun, 15 May 2022 22:20:25 GMT

I’m getting error code e72, have checked the power connection and all is good. Filter is dirty but now bad. What to do?

Re: Nest learning thermostat error code e72

Ryan_G — Sun, 22 May 2022 22:35:39 GMT

Hi lofton,

Thanks for reaching out here in the community.

The E72 message on your Nest thermostat means it is not getting any power to function. This could possibly be an issue with the power from the HVAC not flowing to the thermostat. Also, check the wire at the terminal of your thermostat.

You could also check the fuse from your system.

Let me know how it goes by replying to this thread.

Best regards,

Ryan

Re: Nest learning thermostat error code e72

Ryan_G — Wed, 25 May 2022 22:42:32 GMT

Hey lofton,

I just wanted to follow up and see if you're still in need of help. Please let us know as we would be happy to answer any questions you may have.

Best regards,

Ryan

Re: Nest learning thermostat error code e72

aatienza — Fri, 27 May 2022 05:46:57 GMT

Hey lofton,

Chiming in to check if you have additional questions or concerns as we will be locking this thread within 24 hours.

Let us know so we can assist you right away.

Thanks,

Archie

Re: Nest learning thermostat error code e72

NorthStar — Sat, 03 Dec 2022 18:36:56 GMT

I am having this same problem

Re: Nest learning thermostat error code e72

fellenbaum — Thu, 15 Jun 2023 22:33:31 GMT

Having the same issue and would like to know where to find the fuse. Filter is clean.

Re: Nest learning thermostat error code e72

Markjosephp — Tue, 20 Jun 2023 19:11:59 GMT

Hello fellenbaum,

Thanks for reaching out to us, and I'm sorry to hear you're also experiencing the same issue. I'd be happy to take a look at this for you.

To isolate:

Please share with us a photo of your Nest Thermostat's wiring setup.
Gather the power readings in the Technical Info settings.
If there's a C wire connected to its base, remove and disconnect it.
- Note: Turn off the power from your HVAC system at the breaker box before touching any wires.
- Once removed, check for any wiring reports and gather the power readings.
- If the report disappears and the thermostat works again, the Common wire is not properly grounded, and you can leave it disconnected until it gets fixed.
Occasionally, fuses burn out due to one or more reasons. If the HVAC fuse burns out, the system may cut off the power to the thermostat and cause an E3, E4, E23, E24, E73, or E74 wiring report.
- Search for the HVAC fuse. It’s usually on the furnace control board.
- You can also check the manual. Fuses can be different for each type of system. You may find a small U-shaped fuse with a number 3 label that is pink or purple-colored.
- Remove and inspect the fuse for any damage.
- If the fuse seems burned or has discoloration, consider a fuse replacement.
- Make sure to reattach any panels on the system.

Please keep me posted on how it goes.

Regards,

Mark

Re: Nest learning thermostat error code e72

Markjosephp — Fri, 23 Jun 2023 19:21:46 GMT

Hey there,

I wanted to follow up and see if you were able to check the details I needed above. Please let me know if you are still having trouble from here, as I would be happy to take a closer look and assist you further.

Thanks,

Mark

Re: Nest learning thermostat error code e72

Marcgm — Sat, 24 Jun 2023 23:39:57 GMT

Hi Ryan,

I'm getting an e72 wiring report Reading on my Nest. It's saying no power wires detected. Rh or Rc wires required. I've pulled off the the knob and the red RH and RC wires look both connected. We have not turned on the HVAC system. And haven't been using the Heat. It was only set to heat. We haven't tried yet setting it to cool. There's no problem with fuses; all the other power in the room and adjacent rooms is on. Can you help me?

Best regards, Marc.

Re: Nest learning thermostat error code e72

Markjosephp — Wed, 28 Jun 2023 22:24:59 GMT

Hello Marcgm,

To better understand this, could you please share your thermostat's wiring setup? Also, gather the power readings in the Technical Info settings.

Regards,
Mark

Re: Nest learning thermostat error code e72

Marcgm — Thu, 29 Jun 2023 00:18:24 GMT

Re: Nest learning thermostat error code e72

Marcgm — Thu, 29 Jun 2023 00:25:51 GMT

Hi Mark, thanks so much for your reply. I sent you screenshots of what you need, I hope that covers it. They are the power readings in the technical info and the thermostat's wiring setup. Please let me know if I can help or provide anything else.

Also, FYI, I had a air conditioning person come out to see the system. He found that there was no power going into the system. He checked the breaker and it is in the on position. He thinks that I need an electrician.

Best regards, Marc

Re: Nest learning thermostat error code e72

Marcgm — Fri, 30 Jun 2023 00:14:21 GMT

Hi Mark,

I want clarify and add that I had an electrician look at my air conditioning system today. The A/C system has power coming to it and there is power coming to the Nest thermostat. For some reason Nest is not working. It appears to be a problem with the Nest.

Best regards, Marc

Re: Nest learning thermostat error code e72

Marcgm — Fri, 30 Jun 2023 14:04:07 GMT

Hi Mark,

Yes, I am still having problems. Other than the details, including screenshots, I have already provided you, do you need anything more from me?

Best regards,

Marc

Re: Nest learning thermostat error code e72

zoeuvre — Tue, 04 Jul 2023 22:19:49 GMT

Hi folks,

@Marcgm, thanks for the follow-up information and I’m sorry for the delayed response.

Please gather your Nest Learning Thermostat's power reading by following the steps below:

To open the Quick View menu, press the thermostat’s ring.
Choose Settings.
Turn the ring to highlight Technical Info then press the ring to select it.
Select Power.
- Battery
- VOC
- VIN
- IIN

@fellenbaum, I want to check if you managed to see Mark’s response. Please let us know if you still have questions or concerns, as we'll be willing to assist you further.

I’ll look forward to your responses.

I appreciate your help, Mark.

Best,

Zoe

Re: Nest learning thermostat error code e72

zoeuvre — Sat, 08 Jul 2023 21:49:14 GMT

Hi everyone,

I want to check and see if you are still in need of any help. Please let me know, as I would be happy to assist and answer any questions you may have.

Thanks,

Zoe

Re: Nest learning thermostat error code e72

praneeth111 — Sun, 09 Jul 2023 15:37:34 GMT

Hello,

I'm having the same issue as well, everything looks good but the thermostat is now showing E72 error code for the last 4 days.

Re: Nest learning thermostat error code e72

Jenelyn_O — Sun, 09 Jul 2023 17:27:00 GMT

Hi praneeth111,

Were you able to try the troubleshooting steps that Mark provided above? You can check out this support article for additional reference.

I appreciate your help, Mark and Zoe.

Best,

Jenelyn

Re: Nest learning thermostat error code e72

Marcgm — Tue, 18 Jul 2023 20:56:35 GMT

Zoe, I already provided mark with the information that you've requested. Can you see it? I've gotten very frustrated with the responses I've gotten to my request for help. So far I'm thinking that this is just a waste of time. Can you call me and we can discuss? ###-###-#### is my cell phone in Boston Massachusetts. Best regards, Marc

Re: Nest learning thermostat error code e72

praneeth111 — Sun, 09 Jul 2023 22:16:34 GMT

Hello,

Issue is resolved now, but I had to go through below

1. remove Nest thermostat and install old Honeywell thermostat
2. can see that Honeywell thermostat is working
3. removed Honeywell thermostat and installed Nest again
4. Nest also started worked again

At this point, I'm not sure why Nest stopped working in the first place