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Heat link not turning on

Community Member

I have a 3rd Generation Nest Learning Thermostat. Some time ago, I got a message saying that "It looks like your Heat Link is off." I didn't think much of it as I didn't need heating at the time, but today I tried to turn on the heating and realise that the heat link is completely dead. I am not able to turn it on and not sure what to do.


Can someone guide me?


Community Member

Does it light up when connected with USB cable?

Community Member


I’m in the same boat, I connected USB cable to the Heat Link and a yellow light appeared. I pressed the button for 10+ secs and then the light went off. 

I have H71 error code on the thermostat & I am unable to connect them together. 

Can you help me? 



The USB connection will not make your system work, all that does is confirm there is a possibility of repairing. A yellow light shows there is a good chance of a repair.

You have a common problem where a component has failed, and you either need a repair or a replacement Heat Link.

They fail due to a poor quality component, and Nest have had hundreds of issues. You are not alone, and in the next few weeks this forum will be swamped with users with the same problem.

I don't even know how to connect a USB cable to the heat link. It looks like a rounded rectangle white box.