Since July 25 my Nest Thermostat (3rd Gen) can no longer connect to heatlink.

[TrevorNicholls]

Around mid-July 2025, my Nest Thermostat stopped connecting to the Heat Link. I tried all available troubleshooting steps, but the issue could not be resolved.

I eventually ordered a replacement unit, which arrived on 14 August 2025. This initially worked fine, but after the overnight software update to version 5.9.5-2, the same connection issue reappeared.

The thermostat was originally connected to my existing Heat Link (software version 2.1.2-1). I have also tried connecting it to a brand-new Heat Link, but this was also unsuccessful.

I’ve seen reports from other users of similar problems since the July 2025 software update, but I haven’t found any specific solutions beyond the standard troubleshooting steps.

At this stage, I believe my original thermostat is still functional, but I can’t confirm as I’m unable to access the settings menu—it's stuck on the Heat Link connection screen, preventing me from performing a factory reset or clearing settings.

Could you please advise how I can:

1. Access the settings menu to reset the device.

2. Resolve the connection issue following the software update.

Thank you,

[sicsacol]

Hi @TrevorNicholls,

Thanks for posting on the community page. I understand you're having difficulties connecting your Nest Learning Thermostat (3rd gen) to your Heat Link after a recent software update, and that now you can't even access the settings menu as it's stuck on the Heat Link connection screen. I know how concerning this may be, especially since you've already replaced it and the issue persists. I appreciate the information you've shared and your troubleshooting efforts. Don't worry; let's work together to get this resolved. To better support you, I have some questions:

•  What's the light status in your Heat Link? For more information about your Heat Link's light, please check out the next article: Heat Link lights and what they mean.
• Are there any error codes or messages in your Nest Thermostat display when it's stuck on the Heat Link connection screen?
• How far is your Nest Thermostat from your Heat Link?

Any additional details you can provide will be helpful.

Regards,
Jonathan

[TrevorNicholls]

Hi Jonathan,

Thanks for the response, I did manage with some fast work to clear the settings between a hard reset and the heatlink connecting loop, made no differance and I gave up and left it overnight trying to conenct and in the morning it seems to have connected?? I has left it connecting prior to this for a few hrs so not sure what has changed.

It has disconnected once since then but reconnected after a reset. Not sure what is going on but for now it is ok. 

To answer your questions the heatlink and a slow blinking blue light and the error code was H71.

The only possible thing I can think was there was an unknown issue with DHCP/DNS server I have (use ISC on a Rasberry Pi), this was powered cycled as I moved some stuff about but was having no issues I was aware of and was working fine.





Did not change anything

[sicsacol]

Hi @TrevorNicholls,

Thanks for your response. I'm glad to hear that you finally got your Nest Learning Thermostat (3rd gen) connected with your Heat Link by factory resetting it and leaving it overnight to connect. I appreciate that you've taken the time to answer the questions. As a recommendation, please continue to monitor your Nest Thermostat's behavior to ensure everything continues to work smoothly with your Heat Link.

Please let me know if you have any further questions.

Cheers,
Jonathan