Valiant Ecotec Plus 837 Central heating stuck on ignoring thermostat

[Essexdrew]

Hi all, can you help ?
Have a Valiant Ecotec Plus 837, the central heating runs all the time ignoring the roomstat.
Hot water is fine
No error codes
When i look at the control panel the RAD picture is visible.
When set to on via timer function the heating switches on and off but ignores the roomstat, if the boiler is set to comfort mode CHS runds all the time depending on what I set the flow temp at.
I have seen a similar thread to this on a Valiant where the fix was to chnage the PCB anyone have any thoughts ?
Cheers
Have just checked in installer mode and with heating on and stat not calling for heat it is showing 0 ( open ) Have now set stat to call for heat and it still shows 0 (open) could this be a stat problem ?

 

[stem]

What make / model of room stat do you have?

 

[Essexdrew]

Its a SALUS, just had the front off the boiler and unplugged the two wires from the stat putr a meter across them and can see a full short when i make the stat call for heat and then open circuit when i stop it calling. Looks like its pointing to the PCB ?

The diag mode on the boiler reports as open when the stat is calling for heat and when it isnt.

 

[stem]

That's the make, but not the model. There are several versions of the Salus, so I was hoping you would be a bit more specific.

Anyway, usually Salus thermostats have terminals marked 'Com' and 'NO' if you want to test it and are are able to do so safely, turn off the power, open up the room thermostat and have a look. If that's what you have, remove the wire from the 'NO' terminal and isolate it safely. Then turn the power back on. If the radiator symbol doesn't come on now, then the thermostat is the cause of your problem. If the heating still does come on the fault is elsewhere.

 

[Essexdrew]

Hi there, its a RT300.

 

[stem]

OK it's L and SL then:

If you want to test it and are are able to do so safely, turn off the power, open up the room thermostat, remove the wire from the 'SL' terminal and isolate it safely. Then turn the power back on. If the radiator symbol doesn't come on now, then the thermostat is the cause of your problem. If the heating still does come on the fault is elsewhere.

 

[Essexdrew]

Hi Stem, just found a post you posted a couple of years ago about how to wire up the Salus receiver to a Vaillant ecotec plus. I followed your guide and within minutes it was all working !!
It turns out that the boiler had never actually been wired up correctly to the thermostat in teh first place, now have fully working CHS that is obeying commands from the room stat.

Thanks for talking the trouble to reply

 

[stem]

Good, glad to hear that you resolved it.