Historical list of error messages ?

[Johnabe]

Hi all. I’m getting a “no power to RC wire” error regularly, but intermittently, with related heat shut off for rough 2-3 minutes. I’ve researched the likely root cause to a “condensate drain trip switch” issue, but since it’s on and off and we are still getting to temp, I haven’t DIYed or called for service yet. What I am looking for is this - is there / where is there in the app, a historical list of these error messages logged ? I’d like to see and share whether it’s twice a day during morning heat up or 20 times throughout a day. I’ve gone around the app but can’t find such. Comments please !! Thanks 

[harryjal]

It sounds like you’re tracking the issue carefully, which is smart before calling for service. Intermittent problems like this can sometimes be linked to underlying environmental factors, not just the equipment itself. In homes with high humidity, for example, a persistent mold issue  can sometimes affect HVAC components or trigger safety sensors like the condensate drain trip switch. Keeping a historical log of errors, combined with regular inspections, can help pinpoint whether moisture or mold is contributing to repeated trips.

[Johnabe]

Thanks for this feedback @harryjal ; do you know where in app I can find a list of these errors incidents so I can consider their frequency ?? Thanks! 

[harryjal]

Most apps show these under System Events or Diagnostics, but some don’t provide a full historical log. If the app lacks it, keeping a manual record of each occurrence is the best way to track frequency and spot patterns.

[austinpatrew2]

Makes sense you’d definitely want a way to track those intermittent errors before calling service. A historical log would help spot patterns easily. 

[Johnabe]

Appreciate thoughts @austinpatrew2 Here’s an update- still couldn’t find anything in nest app that would show me the error history - but nest sorta made me load google home and it has an “Activity” button that shows timestamps “heated for 7” minutes and then a time gap of 3 minutes and then “heated for 5 minutes”, so you can guess that 3 minutes was an RC power outage (error code on nest times out visibly). If I figure out how to attach pics I would show such, but for now I’m carrying on 

[Johnabe]

 

[Johnabe]

 

[BeulaA]

Hi @Johnabe,

Thank you very much for contacting the community! I understand you’re intermittently receiving an "E73 No Power to RC wire" error on your Nest Learning Thermostat (3rd gen), causing short 2-3 minute heating interruptions. You suspect the condensate overflow switch is tripping and self-resetting, but you’ve delayed repairs since the system is still technically maintaining the set temperature. I appreciate the screenshots and the detailed research. I know how important it is for your thermostat to function properly, don't worry, I'm here to help!

Currently, the only way to view the history of these events is by checking your Energy History. This will show you exactly when the system turned on or off; however, please note that it won’t specifically 'tag' or label the 'Rc' error events individually.

Therefore, I would like to ask a few questions to provide you with the most accurate troubleshooting steps:

• When did the issue start?
• Is this a new installation?
• When was the last maintenance check for your HVAC system?
• Have you experienced any power outages in the last few days or weeks?
• What type of heating, ventilation, and air conditioning (HVAC) system do you have?
• Could you share a picture of your wiring with me?

In the meantime, I recommend trying the following steps:

• Check that the wires are fully inserted into the terminal and the connector buttons are securely pushed down. This ensures proper wire connections. For reference, you can check out this article: Troubleshoot thermostat power issues during hot weather (E3, E4, E23, E24, E73, E74, or E195 help co... Important: Before touching any wires, turn off the power to your HVAC system at the breaker box.
• Check the power readout under Settings > Technical Info > Power and send the information shown there.
• Make sure the circuit breakers are switched on.
• Check the condition of the HVAC fuse.
• Check the condition of your air filter to see if it is dirty or needs to be changed.

@harryjal and @austinpatrew2 thanks for your help on the troubleshooting provided.

Keep me updated.

Regards,
Beula

[Johnabe]

@BeulaA , thanks for weighing in here. Complicated enough scenario. I came here just looking for the click stream that would give me error history. Still don’t see in the Nest app (energy history or history) but as I said associated google home shows an equivalent under Activity so I’m good there. The real underlying issue ?? Harder to assess. I gather there are half dozen furnace mechanical safety features and triggers that can result in shut off and “no RC power”. I’ve had a furnace service and they couldn’t land on it. For example (Sorry this is caps but it but / paste as such) - HIGH LIMIT switch, GAS PRESSURE, FLAME SENSOR, PRESSURE SWITCHES, A/C COIL, HEAT EXCHANGER FAILURE. They also checked the Condensate Drain suggested by AI. We’re going to install new High Limit switch and go from there. SO … I don’t want to concern this forum with something that is mechanical and is only loosely reported by Nest. At least Nest showed an error and Home app gives a related history which my previous analog thermostat didn’t do. I believe it’s an old problem just recently highlighted by new Nest. Fair enough. 

[BeulaA]

Hi @Johnabe,

Thank you for your response and for the information provided. After installing the new high limit switch, if you're still experiencing the same issue, please feel free to reach out here so i can provide further assistance. 

Regards,
Beula

[Johnabe]

Ok all @BeulaA @harryjal , this is fixed now. To recap for anyone’s interest, the nest thermostat showed “no power to RC” error intermittently. Google Home “activity” showed list of furnace power on and offs. it was one of a handful of mechanical safety shut offs. Service called in. While AI suggested “condensate trap” was a common root cause, that was found fine, and “false-positives” from a “high limit switch” was determined to be it. FYI the high limit switch may have been compromised by debris in the system, keep those filters clean. So thanks to the Nest and Google Home functions for helping highlight this issue for mechanical repair. 

[BeulaA]

Hi @Johnabe,

Thanks for the update! I’m glad to hear that the issue has been resolved. If you have any questions in the future, please don't hesitate to let me know.

Regards,
Beula