Heat link is maybe dead?

[EricBE]

Hello,

I have a 3rd-generation Nest Thermostat (bought in 2020, Nest Learning Thermostat 3rd Gen (EU) Stainless Steel) paired with its Heat Link system.

This morning, I noticed that the heater wasn't working, and I realized there was no light on the Heat Link module. At the same time, my Nest Thermostat displayed this message before shutting down due to a lack of power:

H72 HEAT LINK: The power to the thermostat is off. Learn more at nest.com/h72.

It seems the Heat Link is not powering on. I checked the power supply to the Heat Link and confirmed that it’s receiving 230V (I’m based in the EU). However, even after pressing the button for more than 30 seconds, there’s no response.

To troubleshoot further, I connected a power bank to the Heat Link (after removing the cover, of course). The device powered on, and the LED light on the top turned on. However, even when I press the large button, the heater does not seem to respond.

As soon as I disconnect the power bank, the Heat Link goes dark again, despite the fact that the N and L terminals are receiving 230V.

Is the Heat Link dead? What steps should I take next?

Thank you for your help!

[EricBE]

BTW, when an external power source is plugged to the Heat Link, all LEDs are turned on.

[Frustratedddd]

Just to confirm.... Are you saying there are NO lights on the Heat Link when powered with 240v?

I assume from what you are saying, you have plugged a USB into the Heat Link micro USB port and 3 lights came on, correct?

[EricBE]

Yes, just to clarify: everything was working perfectly before, and there was no intervention on the Nest, Heat Link (HL), or boiler—especially since, as you can imagine, this occurred during the night.

What concerns me is:

1. The HL is powered by electricity (230V) but no longer displays its usual light as it did before. (I confirmed that electricity is present with a multimeter.)

2. My Nest, which is connected to the HL via wires, is not receiving power and has shut down (though I was able to turn it on using an external USB power bank).

3. Similarly, the HL powers on (its LEDs light up) if I connect it to a USB power bank. However, nothing seems to work properly. I attempted to use the large button on the HL, hoping it would send a manual command to my boiler, but it had no effect.

Question: Is it possible that the HL will not function at all if there is an issue with the boiler? What I don’t understand is that the boiler and HL are not sharing power - even if there was an issue on the boiler, why it would not turn on?Moreover, it seems odd that both would fail simultaneously. (For reference, I have a BOSCH GC 7000iW 35/23 boiler.)

[Frustratedddd]

Ok, again to confirm.

1. Are there any lights on the heat link with normal 240v? Yes/No?

2. Your display will not have any power, if powered by wire, if there is no 240v power at the H/L

3. Again to confirm, are you plugging a USB power source into the H/L micro USB?

[EricBE]

 I will answer with short answer (when possible):

1. No
2. it s not a question. 
Your display(=I guess thermostat) will not have any power, if powered by wire, if there is no 240v power at the H/L => There is power at the N/L pins - however the HL seems not to bring back the electricity (12V) to the Thermostat. My Nest is connected by wires to the HL.
3. yes 

[Frustratedddd]

OK, simple answer your Heat Link is dead, if no lights on the Heat Link and you have a confirmed 240v supply. Common problem as a small component has failed.

Your display will not have power from T1-T2 if the component has failed.

Regarding plugging USB not the Heat Link, WHY would you do that? Where in the manual does it say plug into the USB to power up?

[EricBE]

Hello thank you BTW for your time @Frustratedddd .

My advice for people with the same issue : just contact the Google Support Service directly to find a solution.

[ChristelleTorp]

i think no

[EricBE]

If it s not dead, why it does not turn on ?

[Frustratedddd]

No idea what this means ------- ''If it s not dead, why it does not turn on ?''

[EricBE]

it means  : 
If the HL is not broken or with a malfunction then why the HL does not
+ turn on (LED on) 
+ provide electricity to the Nest Thermostat

English is not my mother tongue ... sorry if you do not get everything I said

[GabrielaG]

Hi  EricBE,

We appreciate you contacting the community. I am sorry to hear that your heat link is not working as expected. I will be happy to help you this time.

To get a better understanding of the situation, please help me out by answering the following questions:

• When did the heat link and thermostat get installed?
• Have you recently had service or maintenance on your electrical, plumbing, or heating system?
• When you connect it to the power bank, what color light does it display?
• When did the issue start?

Let me know if you need further assistance. 

Regards,

Gabriela