Linea 28 keeps going to combustion mode error CO

[Gasguru]

Is it possible the "spindle" is jamming against the front panel or the little plastic cover piece?
What happens if you remove the spindle cover does CO stop coming on.
You could always try toggling the switch several times in case it is a little sticky...it's only a push button.

https://cdn.ecommercedns.uk/files/4/221104/8/9068148/10020477.jpg

 

[Max2020]

Is it possible the "spindle" is jamming against the front panel or the little plastic cover piece?
What happens if you remove the spindle cover does CO stop coming on.
You could always try toggling the switch several times in case it is a little sticky...it's only a push button.

https://cdn.ecommercedns.uk/files/4/221104/8/9068148/10020477.jpg

I haven’t tried that though i am pretty sure it was not in contact with the push button.
I have removed the small plastic cover from it to check overnight.

 

[ianmcd]

If you have young kids, be aware, that when the Control override is activated the radiator temp will not be controlled and will get extremely hot, they wont touch them twice though

 

[endecotp]

An odd thing about that display PCB is that the three main knobs are all the same, i.e. a plastic knob that connects to a potentiometer (aka variable resistor) on the PCB, even though the middle one is not a continuously-adjustable control but rather a three position CH+HW/off/HW switch. So the little microcontroller on that board is looking at the voltage from that potentiometer and comparing it with some thresholds to determine which of the three positions it is in. That could go wrong if that potentiometer got dirty.

Now I’m not totally sure about the CO button - it’s a few years since I looked at it - but I think that works by changing the same voltage. (It’s not difficult to observe where the PCB tracks go; unfortunately it’s not on the side we can see in the picture gasguru linked above.) If I’m right, the microcontroller is looking at this voltage and determining one of four states: off, CH+HW, HW, and CO.

So if you’re seeing CO mode when you’ve not pressed the CO button, it’s possible that the problem is with that middle control knob. If you have some contact cleaner (or isopropyl alcohol?), try to spray it inside the potentiometer and turn it back and forth a few times.