Nest heatlink appears to be dead

[tommyhayes]

I think i have the 2nd gen nest thermostat. It's not controlling the boiler as of last night.

No led active on the heatlink and when i power off the boiler from the main switch I just get 1 yellow/amber blink.

I used to be able to power on the boiler using the push button switch on the heatlink but it's not doing anything now.

Any ideas folks?

[Frustratedddd]

You are not getting any lights at all on the Heat Link even when th ebutton is pressed, corect?

Try pressing the button and holding down for 30+ seconds, and see if you get a blue pulsing light.

Should you get a blue light, then you will have to pair the set again, but see what happens.

[DragosC]

Thanks for letting us know,  @tommyhayes

Could you tell me please when did the situation start occurring first and when was the thermostat installed?

Also, please answer to the following questions:

Are there any lights on the Heat Link? Does the boiler activate when calling for heat by pressing the Heat Link's button to activate Manual Mode?
Are you seeing any wiring report or error on the thermostat and/or the app?
Have you had any recent power cuts in your area? If yes, has the power been restored?
Have you recently had service or maintenance on your electrical, plumbing, or heating system?
If yes, how long was the power off for? (Be specific.)
Could you tell us please if you've checked on the breaker switch and fuse box?
Any blown fuse in there? Have you tried to turn the breaker switch off and on again? Any difference?

[tommyhayes]

Thanks for getting back to me.  

I was getting one single yellow flash.

Last night I checked for msins voltage on the nest and was only getting mV. When I probed again I heard a crackling noise inside the nest.then suddenly I get mains indication on my DVM. Its been fine since but I just hope it doesn't come back to bite. 

[Frustratedddd]

Crackling noise is not good!

First make sure the terminations are correct, and not loose. Tighten with a screwdriver to double check.

[tommyhayes]

I agree crackling is definitely not good.  It seemed to be coming from inside the nest as opposed to the wiring. Ill isolate power later when I'm home and check the wiring. It's installed though at least 2 years ago and it hasn't been touched.  I'll report back.  

[Frustratedddd]

Yes that would be best.

The crackling could be the relay breaking down, I have had that in the past. That is usually when the contacts are overloaded. What do you going out, or what are you operating?

[tommyhayes]

Just 2 motorised heating valves. As I said for the last 2 years ....no issues

[tommyhayes]

OK I've found the problem. Where the live mains connects in there were 2 wires. One of them just pulled out when i gave it a light tug. I tried inserting both again after opening up the terminal screw fully but could not get the terminal to tighten up against the 2 wires so i had put 1 wire in there and make the join with a terminal lug outside....no other option. I think the terminal might have been damaged on install or they're just not big enough to clamp down on 2 wires. Anyway all good now. 

[DragosC]

Thanks for letting me know @tommyhayes and thanks for your help @Frustratedddd.

I'm glad it's been sorted out. I'll leave this thread open for a couple of days in case anything else comes up. 

[Frustratedddd]

There you go always best to check the obvious first.

Regarding the damaged terminal screw: What I do is remove the faulty screw which is tricky by this method.

Screw the faulty one down so it just tightens, then insert a very small screwdriver or anything small enough to go into the connection hole. Keep the pressure on the screwdriver or whatever you are using, then with another screwdriver, undo the screw while keeping the the pressure on the inserted screwdriver. You will find the screw will come out, and you can then do the same method with a terminal you are not using ie OT1. Swap the screws over, and with luck you might get a good connection. Works most of the time, if your happy with your connections, then perhaps leave be.

Glad to see you are now up and running.

[tommyhayes]

Good idea with the screw 

[AlexD]

Thank you for your suggestion. Do make sure to reach out to us before attempting any work on any part of the thermostat. Certain actions especially during the warranty period could void it. Just make sure to reach out here or over any of our support channels so we can look at all the possibilities. 

[george_t]

It's been a while since this thread was last updated so I'll go ahead and lock this thread. If you're still experiencing problems, please feel free to start a new thread and we'll be happy to help.