Central Heating Wiring - Weird Stuff Happening

[D_Hailsham]

The first is where the CH & HW are OFF at the Timer, but when the Room Thermostat calls for heat the Boiler fires up.

So voltage must be getting through the room stat when it shouldn't. This points to a fault with the programmer or the programmer wiring

The second is where the CH is ON and HW is OFF - Room Thermostat is NOT calling for heat but the HW thermostat is - this results in the boiler firing up but the valve stays at H meaning!

The only way I can see this happening is also due to a faulty programmer/wiring.

Remove the prgrammer from the backplate and check if you can replicate the faults.

Check out Mid-position valve operation and fault finding