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3rd Gen Heat Link - no lights

Community Member


I have had my Nest 3rd Gen since Jan 2020 (from Amazon) and the heat link has just failed. 
there is voltage present at the heat link but no lights and no connection from the thermostat to the heat link. 
How do I go about getting it replaced???

Considering a switch over to Hive…


Community Member

I have exactly the same problem. Suddenly my heat link failed. No lights and no response when pressing the button. I purchased it in November 2019 (from Amazon too) and it has been working since December 2019. It seems to be a common issue, as there are tons of posts talking about it. Any clue on how to get a new one from Google (still under warranty) will be welcomed.

The first thing I would do is contact Amazon, as they are the retailer you purchased the item from. They are the first in line for the faulty item.

Secondly, as I have listed so many times ring Nest.

Community Member

Same issue. My 3rd Gen Heat link failed this morning and is completely unresponsive. I have no heating or hot water. Any advice on how to fix / replace quickly would be welcome.

Same as above.......

I am setting myself a challenge to see how quick I can get my heating back up and running, due to a faulty Heat Link with no lights.

My fault is, No lights on the heat link, power to the heat link, installed 2019 by a plumber, no power cuts, and no work has been done in the property.

Let us see who has the heating up and running first. I will go down the avenue I have stated so many times on here, by direct contact. You 3 above see what happens on this forum.

I will start at Friday 22nd @ 11.20am

By the way I have done this several times, I am just proving waiting for answers on here is pointless.

The first update on my progress... Friday 22nd Oct - 12.35

Contacted as stated at the time, just received the confirmation of the replacement at 12.29.

Today is Friday, not good for the weekend postage as you will be aware, so I would think I am looking at the replacement arriving on Monday/Tuesday

How are you 3 getting on?

Community Specialist
Community Specialist

Hi @Butch10 , @FrascoHurtado , @OJ . I am sorry to hear you are facing difficulties with your thermostat devices. 


Make sure to check all breakers and switches if you have not already, to make sure nothing has tripped. Also check the boiler as it can have a separate switch on it. Confirm the boiler has power, it should have a status LED or display that turns on.


If you checked and the power looks good try and power cycle the Heat Link next, if you're comfortable in doing so. Turn the power to the Heat Link off for a few minutes and turn it back on. See if it has any reaction after if you press the button on it. 


Hi @Frustratedddd , I am happy to hear you already managed to get in touch to get things back on track. If there is anything that I can assist with, make sure to let me know.


Best regards,


Community Member

Electrician said there is power going to the heatlink but it is not lighting up.  Can I presume it's faulty and switch it for new one.  Only have it 3 and a half years. Thermostat is ok 

The second update on my progress... Friday 22nd Oct - 15.51

Friday afternoon, and the replacement has been shipped.

You 3 still getting on OK, or still waiting for a reply for the muppets on here?

I have just run the heating cables (2 & 3) through a switch external to the heat link - linking them together would give permanent heating, the switch allows me to choose when it’s on or off. 

I contacted Google and they are sending me a replacement heat link, this will get me though until it arrives 

Community Member

I have just run the heating cables (2 & 3) through a switch external to the heat link - linking them together would give permanent heating, the switch allows me to choose when it’s on or off. 

I contacted Google and they are sending me a replacement heat link, this will get me though until it arrives 

Ah at last, contacting direct gets results.

Remember by connecting 2-3 together will give heating, but not tempreture control. Keep an eye on the room temp, as you have to do that manual now.  Sucking eggs and all that!!

I am aware but appreciate the heads up 👍🏻

Great you are aware, but can you imagine the people that are not, and will be sitting at home watching the TV in their undies!!!!!😂

The Mrs would definitely do exactly that 😂 - hence the installation of the external switch to make it even easier…!!

Third update on my progress... Saturday 23rd Oct - 12.35

Confirmation of the replacement Heat Link coming Monday 25th Oct.

You other 2, FrascoHurtado and OJ still getting on OK, or still waiting for a reply from AlexD?🤣🤣🤣🤣

Community Member

Mine has somehow arrived today so my temporary fix was much more temporary than I had imagined!!
Now comes the fun part 🙂

There you go, get hold of the correct people and your laughing.

Setup/installation is easy, but when you get to pairing, remember yours is not a matched pair anymore. You will have to enter the code found on the left hand fixing screw. You may find if you have a wireless setup the screen freezes, if that happens enter the code, and when you get to the ''Connect', leave for a few minutes, then connect. Wired setups are fine.

FrascoHurtado and OJ, how you getting on, still waiting or have you called yet?

Installed correctly and the new heat link is working perfectly - apart from the fact it won’t connect wirelessly to the thermostat…

I have tried wiring the stat in directly and it works perfectly. 
I have also tried every possible reboot and reset of both devices. 
Could they have sent me a heat link with a faulty wireless module?

Anything is possible, but I would think they have been tested well. The big button, does it the words Nest or blank on it? Blank is good.

When the Heat Link is hard wired the pairing will be done without a hitch normally, but you still have to pair wireless. To do this, you will have to go Settings - Equipment - Heat Link, then Wireless. You will HAVE to use the 6 digit entry code found on the Heat Link cover by the screw, or on the left hand fixing screw.

The reason being as mentioned it's not a matched pair anymore. You will have to use the 'Replace Heat Link' method to pair.

Have you tried all that?


It is blank and I have tried the ‘Replace Heat Link’ option (and every other option going 😔). 
I’ve even carried out a full factory reset of both the stat and the heat link…. gutted 😡

I take it the blue light is pulsing? Just to make sure you have set the Heat Link to default, press and hold the button for 30 seconds, until you get a blue light pulsing, then do exactly the same again. You need to reset twice.

Just make sure you have the entry key correct. Make sure the entry key is the same number on the lid as on the fixing screw. make sure if you have a zero you have not put in a letter 'O'.

I would be very suprised if the Link is faulty.

There is one other test if you are 100% sure you have tried all the ways, and that is to double check the entry key is correct. By that I mean the numbers on the lid and fixing screw may be the same, BUT I have known the real number is different. The ONLY way to prove is with your PC. I will explain if you have covered all the above first.

I had not been carrying out the ‘double reset’ - I have not done so but the result is the same…

I have checked both entry key positions and they do match (and I have been using a 0 instead of an O)
I assume I need to connect to the USB in heat link using a TeraTerm or similar?

Sounds very odd to me, but if you can try this to confirm.

Plug usb into the service port on the right hand side of the Heat Link, and into your PC. The drive should come up in your PC as 'Nest', Open the drive,and look along the words until you can see th eentry key. Check the number is the same. Should it be different, take note of it and try that. Very rare, but has happened.


I have tried 2 different laptops and 2 USB cables and I do not get any additional drives when plugging in to the nest….?! 😔

Plug it into your PC, and press and hold the button on the Heat Link until the light goes out

Open the Info folder, and look for ''Pairing Key''

By the way, have you noticed how the Google idiots are rushing to help you??

Can you see why I get so frustrated, because of the jumped up Google advisors, that only say something when it's easy. They are the experts for goodness sake and not one of them here to help you. Pathetic.

By the way how you doing FrascoHurtado and OJ, keeping warm???

Community Member

Aha, it worked this time.....

<string>Amber box-app</string>
<key>Account ID</key>


402MDU is the same key as on the device itself and is still not working


Yes that's the correct entry key in that case, worth double checking though. Silly question, have you tried a 'O' instead of a zero?

Let me get this right...................You have hard wired the thermostat back to the Heat Link?

You have a connection working wired and the stat is operating the Heat Link?

You have gone into Settings - Equipment - Heat Link - Wireless, then clicked Replaced Heat Link and entered the entry code?

Then after you have done that what does the screen say, or does it just search and search until it says unable to connect wirelessly.

Make sense?

Community Member

I have, it shows as an instant error....

I really appreicate your help with all of this - as you say, the google guys on here have been less than helpful!!!

I'm not normally beaten by these Nest things, but this is trying my patience, and yours must have gone!!!

Where are you located?

Community Member

I tried hard-wiring the stat directly to the heat link and it worked perfectly that way. 
I then did as you say and tried selecting wireless (on the wired page) - it says unable to connect and then goes back to wired operation as normal. 

I have since disconnected the stat and put it back on the stand and carried out another full factory reset on both - when not hard-wired I get the H71 error code. 

I’m based in Crawley, West Sussex. 

OK, that could be the issue, the stat is confused now I think.

When wired and connected to the Heat Link and working correctly, you are halfway there.

Then, go to Settings - Equipment - Heat Link, BUT try 'Reset Pairing'

That may not work, but worth a try first. The reason being, although it's a none paired set anymore, the reset pairing should work.

I think to start from fresh would be the best bet. ,

I would hard wire, forget the wireless for a moment, then reset to factory settings, while hard wired.

Still hard wired, go through the process but ignore the wireless still. The end of the setup, you will notice the Heat Link will NOT work until you turn the stat dial to the right,above the current tempreture setting. You will then hear the Heat link click in.

After you have turned the stat a few times making sure the Heat Link is working correctly, THEN try the wireless part, but try ''Reset Pairing this time''

Make sense again?

You will get a H71 as there is no connection between the 2.

Just as a matter of interest, on the H71 part go down to Tech, and look at Heat Link. What entry key do you have? The new Heat Link one?

If yes, try ''Reset Pairing'', the reason being the code has been accepted.

Community Member

I’m done for tonight now as it has officially broken me (for today), I will try the process you suggest when I get home from work tomorrow. 

It does indeed show the new code and I have tried using the ‘Reset Pairing’ option…. 😢

Ok, you will need to start from fresh when you start.

1st charge the display until it has at least 3.9v, if not plug a usb into the back of the display for 90 minutes.

2nd when charged, hold the display in your hand,and squeeze the display like a hamburger until the house comes on, then release. Do that twice.

3rd when the heat link is hard wired, press the button and hold for at least 30 seconds until you get the steady blue pulsing light, do that also twice.

All parts are now ready.

Follow the instructions on the screen, but ignore the wireless part when you get to that.

When you complete setup, you will have to turn the dial to th eright to hear the heat link click in. do that a few times to make sure you hear the heat link clicking.

Now you can go back and setup the wireless connection as I stated.

I hope that works, as I am convinced there is nothing wrong with the heat link.

Have a good night.....