Nest thermostat wont turn heating off

[GaryA]

My nest 3rd gen thermostat won't turn the heating off.

I have tried with the help desk on many occasions with the same tests and the heatlink still stays as connected with a green light.

I can hear the click each time it is turning off and on from the heatlink however the heat stays on when it reaches the termerature.

I have been told by one asvisor to replace my heatlink but I also have problems finding somewhere to order a new heatlink 

Any help on both things would be great. I am in Northern ireland 

[Frustratedddd]

How long has this been installed?

How many green lights on the Heat Link?

Does the display go from orange to black when you turn the heating down?

Have you tried a full reset?

[GaryA]

Installed around 4 years with a new  heatlink about 3 years ago

One green light on the heatlink 

Thermostat goes organe when asking for heat and black when it reaches the temperature however the heating stays on when it goes black

I'm not sure if o have been talked through a full reset from an advisor yet, how do you do a full reset?

[GaryA]

Also all these issue have only happened after a 14 hour power cut 

[Frustratedddd]

This system has been working OK for the past 3 years since the H/L change, and just started this issue - correct?

You might have a relay stuck by the sounds of things.

Do you have any tester or a neon screwdriver you could check things with?

[Frustratedddd]

I take it the advisor talked you through a restart by pressing the display against the wall until the house shows?

[GaryA]

No but I will also give this a go

[GaryA]

I'm a bit of a novice but I do have a neon screwdriver 

Would a new heatlink fix a relay problem 

I really appreciate your advice thank you

[Frustratedddd]

You don’t have to be a genius to use a neon screwdriver, and it’s a 2 minute job.

You might need a hand, but should be OK.

First make sure your display is well turned down to not calling for heat, the display should be black. Turn to say 14. Make sure you only have one green light on the H/L.

OK undo the screw at the bottom of the H/L and remove the cover. Remember the terminations are LIVE. You will be fine.

You will see terminals marked 1-2 -3, and you should have wires coming out of 2 & 3 . (These are the heating terminals.)

Put the neon driver onto terminal 1, you should see the neon glow bright. Now put the neon driver onto term 3 it should be not so bright. Correct?

Now with the neon on terminal 3, press the H/L button and see if the neon is brighter, like it was on terminal 1. Yes or No?

Don’t alter anything, now put the neon onto terminal 1, has the neon gone dull? Yes, press the H/L button again so the green lights go to only one, has the neon gone brighter? Yes or No?

I hope that makes sense.

[GaryA]

This makes sense and here are my results, I really do appreciate your help, I have answered below 

Put the neon driver onto terminal 1, you should see the neon glow bright. Now put the neon driver onto term 3 it should be not so bright. Correct? bright on terminal 1 and no light at all on terminal 3

Now with the neon on terminal 3, press the H/L button and see if the neon is brighter, like it was on terminal 1. Yes or No? yes this was as bright as terminal one 

Don’t alter anything, now put the neon onto terminal 1, has the neon gone dull? Yes, press the H/L button again so the green lights go to only one, has the neon gone brighter? Yes or No?  Terminal 1 went dull when h/l button was pressed and when h/l pressed again and went to 1 green light it was bright again with no light on terminal 3

[Frustratedddd]

OK, that now proves the H/L is switching the relay for the heating manually, which means your H/L is good for heating. Do you have a combi boiler or system boiler?

Did you notice the boiler coming on when you pressed the H/L button?

The question is now, why the display is not talking to the H/L.

Could you repeat the test above, but instead of using the H/L button to switch, you use the display, by turning from off to calling? When not calling for heat [display black] Term 1 should be a bright light on the neon, and Term 3 dull.

When calling for heat [display orange], Term 1 should be dull light, and Term 3 should be bright on the neon.

This is a long drawn out process, but just trying to see if things are talking to each other.

Should the answer be No to the above, I would do a full reset. Settings, Reset, all Settings.

You will have to go through the performance of setting up the display like you did from new, but, this could be your only option.

[GaryA]

Thank you for explaining all this to me. 

I have a combi boiler system, when calling for heat I can notice the boiler coming on, it just won't go off again unless I switch it off manually at the boiler 

I have done the same test using the thermostat and get the same expected results as you describe so they must be talking to each other 

Just need to work out now why it won't turn the boiler off when it should do 🙈

Am I right in saying then that the heatlink is working fine and they must be a boiler issue or somewhere between the boiler and the heatlink? 

I will also try a factory reset 

[Frustratedddd]

You are welcome, not a problem.

Yes the H/L sounds as everything is working, and talking to the display. The test you have done prove the H/L is switching the contacts, and power is getting to the boiler. Why it's not turning off is a little odd. I would think something is stuck at the boiler end, just a guess I hasten to add. You also say that, when manually turning on with the H/L button you have to manually turn the boiler off after the H/L is back to the one green light.

There could be an issue with the motorised valve in your system if you have one, but by the sounds of things the Nest is working.

I don't think a reset will be of any use, but might be the time to get the boiler man to have a look I'm afraid.

Just to confirm also, the system has been working fine up until recently?

[GaryA]

All working fine until a recent 14 hour power cut after a storm recently 

I am currently going out to the boiler and turning the actual boiler off to get the heating to switch off as that keeps the heating off and just don't touch the heatlink 

Thank you very much for all your help, I am not confident that the best is working and must be a valve issue somehwew with the boiler I assume  but really appreciate all this help, finally confident in the advice I have received 

[Frustratedddd]

The only other thing I would do is the reset as that does clear a lot of issues. You could do that,and it's pretty simple, you would loose all your settings and have to input them again. Having said that, it would confirm the Nest is working.

One other thing, are you wireless connection. wired connection or both to the H/L? you can confirm that by Settings, Equipment,Heat Link,

[GaryA]

I have done the full reset and seems to have not fixed the problem 

I am connected both wireless and wired to the heatlink 

[Frustratedddd]

I would stick my neck out and say the Nest is OK, having said that if I have missed something, then I will take a slap!!

When wired and wireless that proves a signal is getting to the H/L from the display. That means from all your test and reset confirmation, everything is working.

I can only now suggest that the boiler has an issue, either valve or some component issue.

I sadly can't help any further, as without being on site it's very hard to fault find. You have done the Nest end, I think now you will have to give the boiler man a call.

Sorry I have no other easy solutions for you, but like I say the Nest looks good.

Please update on here when you get the problem sorted, and sorry I can't get you out of trouble.

[GaryA]

Thank you very much for everything, you are so kind

Really appreciate all your help and will update when sorted