My problem is that the boiler comes on, there is hot water in the tank but the radiators are cold. Pump is working fine. If i twiddle the living-room thermostat the burner fires up for about 10 secs and then turns off.
If i manually lock open the 3-way valve then then the radiators get hot, but otherwise the 3-way valve stays closed.
I'm thinking that the living room thermostat has gone?? If so, it is simply a case of swapping it out? Or could it be the PCB that has a problem??