Heatlink switch not turning off heating

[Perry01150]

We have just had a boiler breakdown (fan) and on repair the Heatlink just seems to be stuck in the on position.

Manual is it working and the Heatlink to boiler cable is constantly supplying electricity to the boiler.

i can only think the contacts are stuck as there has been no change whatsoever. Is this a common fault? Is there a solution?

[Frustratedddd]

I have seen this a few times, and the only way I could clear the fault was factory reset. You are correct the contacts could be closed.

[Perry01150]

Is the factory reset where you just hold the heat link button till it flashes blue.

i don’t think it’s worked.

[Frustratedddd]

No, sorry I mean a full factory reset of the thermostat. The reset by the button on the heat link resets the heat link, but for some reason I found only a full factory reset worked.
Settings - Reset - All Settings

[Perry01150]

Oh I see let me try

[Perry01150]

No joy. I can hear the heat link click like the connection happening, but the boilers just doing it’s own thing off it’s own thermostat.

God knows whats happened

[Frustratedddd]

That’s not good!

you say you had a boiler repair, I wonder if they have reconnected correctly?

Not an oil boiler by any chance?

[Perry01150]

No Valiant Eco Tech.

the wiring looks the same. I’m still scratching my head as to whether the heat link to boiler cable should show live if the thermostat is saying not to turn the heating on. I’d have thought the connection should be open so circuit not complete.

[Frustratedddd]

The terminals L'', should be live at all times, and if a jumper cable is installed into term 2 from 'L' for example, then that should also be live. The other terms are live depending on call for heat.

I wonder if you have a back feed from the boiler connection?

Which other terms are live?

Standard connection for the heat link is -

Can you take a pic of the connections at the heat link?

[Perry01150]

When I put the mains tester screwdriver on  the 2 and the 3 connections separately they both light up as live.

I’ve no jumper cable either. It’s so weird. 
the 2 and three goes straight to the valiant 3 and 4 as this is the call for heat connection.

I’ll attach a photo tomorrow. Thanks so much for your responses

[Frustratedddd]

2 should be live and 3 should be live on call for heat. What are you getting on term 1?

When the thermostat dial is turned down term 3 should not be live.

Which model have you got, 3rd gen?

[Perry01150]

Hi. Yeah that’s exactly what I thought in my head, which is why it’s such a head mash.

I’ve attached the wired heat link. Yeah it’s 3rd gen.

basically term 1,2 and 3 are all love

 

[Frustratedddd]

This is not complicated, just a process of proving the part is working!

The picture obviously shows the heat link in a testing position, so I assume you are OK with trying something?

1.  Remove the connection from 2 & 3 for the time being

2. Install a jumper cable from L to Term 2

Then see if the heat link is switching, you should have one green light on the heat link to start with.

Term 1 should be live

Term 2 should be live

Term 3 should not

Press the button, all the lights will come on the heat link, then test Term 3 to see if live, and if Term 1 is not.

Simple as that, and if that is correct the heat link is working fine.

You could use the jumper for the connection I have ringed in the picture!

[Perry01150]

Okay. Did the test as you explained.

all terminals 1,2,3 were live when just the jumper cable was connected to terminal 2.

didn’t matter whether the manual heat button was activated or not unfortunately.

Is the switch buggered do you think?

any repair or is it a new unit?

[Perry01150]

Ah I wonder if the engineer has removed the jumper.

i will try this shortly see what it does

[Frustratedddd]

Assuming you have a neutral in the N, and a live in the L, a loop from L to 2 only? No other cables are connected in the box. 

Terminals L + 2 + 3  should be the only connections that are live.

Anything else which is live, ie terminal 1, then the heat link is faulty.

[Perry01150]

**bleep**. I assume there’s no repair?

Do they sell just heatlinks?

[Frustratedddd]

There is a repair, but you need the relay and able to solder. I have managed at times to get them working with a little  brute force. I stripped the heat link down, then gave that relay a tap and a few knocks. Could be worth a try if you are that way in kind?

Nest do not sell them or any spares at all, and if you do find them for sale they are not cheap. About £65

Where are you located as I do have some?

[Perry01150]

Bury in Manchester 

[Frustratedddd]

That's some way from me sadly.

I do have them and if you get stuck, I could get one to you, but they are not cheap as mentioned.

Can you try the knocking trick,and see if your lucky?

[Perry01150]

I’ll give it a knock pay see what happens.

Thanks so much for your help with the thread

[Frustratedddd]

Yes, that has worked a few times for me.

I have also reversed the connections, and power into 1 instead of 2.

I wouldn't mess about anymore, just ring Nest and say the heat link is stuck in the closed position. A new unit will be on it's way.

[JohnDaniel]

I had similar issues with my heatlink, and found a company https://www.electrofixit.co.uk/product/nest-heat-link-repair that repairs these heatlinks at a resonable price. I believe they replaced the relay which got stuck, but i got it back in 2 days and heating now working again.

[Frustratedddd]

I always find it strange when a thread started 2 years ago, then has a reply with a link to a repair company!

I find it even more strange when the company does not show their address!

[AlexD]

Hey there, since the poste of this thread has not been active in a long time I'll be locking this thread. If you have any new issues, updates or just a discussion topic, feel free to start a new thread in the community. Thanks, AlexD.