Ah OK my apologies I missed that, so at least you know now that the thermostat isn't the problem...... Back to the drawing board then.
Ah OK my apologies I missed that, so at least you know now that the thermostat isn't the problem...... Back to the drawing board then.
When the thermostat is 'on' terminals A and B will be electrically connected. And when it is 'off' they are not connected. All the thermostat is, is a simple on/off switch.
By joining the wires in A to B together, it by-passes the thermostat thus taking it out of the equation by making the electrical connection permanently 'on'
Pointing to a pcb fault imo, but this would need to be done by a gas safe registered engineer/competent person (one who is able to complete 26.9 checks afterwards).
If there was a say fan fault yes, however, on this instance no. Get someone who’s familiar with Vaillants. I work on the EcoTEC Pro range almost on a daily basis, so would know what to look for. Maybe if you post a rough location where you are, someone on here maybe able to help.Would a PCB fault not at least show as a F code.
If there was a say fan fault yes, however, on this instance no. Get someone who’s familiar with Vaillants. I work on the EcoTEC Pro range almost on a daily basis, so would know what to look for. Maybe if you post a rough location where you are, someone on here maybe able to help.
It could simply be a bad wiring connection somewhere, even though you've tried bypassing the thermostat itself, the wiring between it and the boiler is still in use, but I guess you've checked that already.
One thing overlooked, you could always swap the wiring to the 24v side, and see what happens?
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