Various issues with my Nest Learning thermostat

[clairewilkins23]

Hello,

I’ve been trying to resolve an issue with our heating system since Friday evening, but unfortunately I’ve made no progress. For the past couple of weeks, the system hasn’t been heating our hot water, so we’ve had to rely on the manual immersion heater, which is both costly and inconvenient.
I’ve attempted several resets of both the thermostat and the Heat Link. When I tested the system, the radiators did heat up, but the boiler began cycling on and off repeatedly, and I was unable to stop this behavior. I tried resetting the thermostat and Heat Link again, but the issue persisted.
As the evening was warm and I couldn’t find a solution, I turned the boiler off completely. The following day, I switched it back on, and it immediately resumed the same pattern—turning the heating on and off erratically.
I’ve now exhausted all the troubleshooting steps I can think of and would really appreciate your assistance in resolving this.
Thank you in advance for your help.

[sicsacol]

Hi @clairewilkins23,

Thanks for posting on the community page. I understand that your Nest Learning Thermostat isn't heating your hot water in your heating system, forcing you to use an immersion heater, and that your boiler is repeatedly cycling on and off when you try to heat the radiators. I know how concerning this may be since you've already tried multiple troubleshooting steps with no positive result. I appreciate the detailed information you've shared and the time you've taken trying to resolve it. No worries, let's work together to get this resolved. To help with that, I have a few questions for you:

• What generation of Nest Learning Thermostat do you have? You can check the generation by following this article: How to tell which Nest thermostat you have.
• Do you have a system or a combi boiler? Is the control on/off or OpenTherm?
• 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.
• Have you experienced any power outages recently?
• Has there been any recent work done on your Nest Thermostat or heating system?

Any additional details you can provide will be helpful.

Cheers,
Jonathan

[clairewilkins23]

Hi Jonathon, thanks for your email.  I’ll try and answer the question the best I can. 

Our thermostat is a 3rd addition learning. 
We have a system boiler, with on/off switch. 
The heat link light is currently green. 

No recent power cuts and we had the boiler serviced at the end of June 2026. 
Please let me know if you need any further information. 

thanks 

Claire 

[sicsacol]

HI @clairewilkins23,

Thank you for your response and for answering the questions. The next step is to perform a simple test to see if the Nest's command is reaching your boiler. This is often referred to as a "click test."

• Stand near your Heat Link and make sure you can hear it clearly.
• Go to the hot water settings on your Nest app or the Nest Thermostat display.
• Manually turn on the hot water to give it a boost for 30 minutes. You can do this from the Nest app by selecting the hot water icon and tapping boost.
• As soon as you activate the hot water, listen very carefully for a clicking sound from the Heat Link.
• After about 10 minutes, turn the hot water boost off and listen for another click.

Also, please check your hot water schedule for your Nest thermostat in the Nest app by following these steps:

• Open the Nest app.
• From the home screen, select your Nest Thermostat.
• Select Hot Water > Schedule.

Please let me know how it goes after trying these steps.

Cheers,
Jonathan