Honeywell ST6400C stopped working when I moved it ... loose wire

[JP_]

Finally got around to sticking my heating controller to the wall today - it's be working fine until now.

After sticking it on wall, it stopped working completely. When positioned carefully, it came on. It worked with the Heating on, but when the Hot Water was turned on, it was turning on/off constantly.

I opened it up and there was a loose wire. I put the wire in the empty one, and heating works, but when hot water turned on, the boiler stops (all lights showing on on the controller). The wire was very close to the other brown as see in the photo, so I thought maybe it came out of there, but that didn't work either.

Assuming dodgy unit now, and have a new one on order (Honeywell ST9400C), but am I missing something obvious?

Video shows it flickering on and off

https://photos.app.goo.gl/5jnNMcewHw8EDrbD6

 

[stem]

As is stands in your photo, there's no live wire connected to L so it won't have any operating power.

The other wires in N, 1, 3 & 4 are commensurate with a heating system fitted with a 3-Port motorised valve (Y-Plan) and terminal 2 isn't used.

However, if the backplate is twisted, not completely flat, the programmer not securely fixed to the backplate with the correct screws (which appear to be present) or the connection pins are worn or dirty, they can still flicker even with the wires connected properly.

 

[JP_]

So, which one does that loose cable need to go into? The one with the grey on the left?

I think my electrician is popping in later to look, but if he can't make it I'll have another got at putting the cable in.

 

[ianmcd]

most likely to be the brown wire that you have made a dogs dinner of connecting into T1 put that into the L terminal and do it properly

 

[JP_]

This is how it is now

Heating works, but as soon as I turn on the hot water, I hear the boiler go off.

 

[ianmcd]

you will have to go to the 3 port mid position valve now and check what positions it moves to with HW on then CH on then both on, when you say you hear the boiler going off does it comeback on again ? there is a short delay when switching between modes but seconds rather than minutes

 

[JP_]

when you say you hear the boiler going off does it comeback on again ?

No, i waited a bit, not a minute, but 10 seconds or so.

 

[stem]

most likely to be the brown wire that you have made a dogs dinner of connecting into T1 put that into the L terminal and do it properly

Looking at the photo, there's that much copper on show, I thought it wasn't connected to anything and just positioned loose in front of T1.

I love it when folks just guess where they think a wire has come from and just stick it in, then wonder why they've blown something up. Fortunately in this instance the OP put it in with another live.

 

[ianmcd]

No, i waited a bit, not a minute, but 10 seconds or so.

give it a bit longer, there is an on off lag when you switch between modes, souldnt be more than 30 seconds then if working correctly will come back on

 

[JP_]

Tried that, waited 3 minutes. As soon as i switched the water of, boiler came back on.

How do i check the 3 port mid position valve?

Also, is this an electrician job or heating engineer?

 

[JP_]

Looking at the photo, there's that much copper on show, I thought it wasn't connected to anything and just positioned loose in front of T1.

I love it when folks just guess where they think a wire has come from and just stick it in, then wonder why they've blown something up. Fortunately in this instance the OP put it in with another live.

But it still doesn't work.

 

[terryplumb]

Reading through your posts leaves me somewhat confused ,correct me if I am wrong ,but as I understand it , your central heating works fine when selected only. However ,if you then select hot water as well as c/heating ,the boiler goes off and remains off. If you then turn h/ water off, the boiler fires up again . Is that all so ?
If so ,turning off c/ heating at programmer ,and selecting h/ water ON, only ,does boiler fire up ?

 

[ianmcd]

How do i check the 3 port mid position valve?

post a pic of it so we can see which make you have

 

[JP_]

Reading through your posts leaves me somewhat confused ,correct me if I am wrong ,but as I understand it , your central heating works fine when selected only. However ,if you then select hot water as well as c/heating ,the boiler goes off and remains off. If you then turn h/ water off, the boiler fires up again . Is that all so ?

Yes.

If so ,turning off c/ heating at programmer ,and selecting h/ water ON, only ,does boiler fire up ?

No, boiler stays off. I will double check when it is quieter, or I get up in the loft where the boiler is, later, but can't hear it coming on.

 

[JP_]

I assume this is the 3 port mid position valve?

The switch didn't move when I tried changing HW on/off, heating etc.

Is this a job for the electrician that moved and rewired the Honeywell, or a heating engineer?
I am guessing the heating engineer would be a better bet now?