A similar problem to many on here. The CH is flat out whatever the system settings, unless the boiler is off.
Gloworm condensing boiler, Grundfos pump and Danfoss controls (FP715 programmer, room stat; HSV3 and HSA3 comprise the valve assembly)
When the HW is on so is the CH and CH will not respond to the room thermostat nor the manual on/off on the programmer. HW will respond to the programmer and the cylinder thermastat but also will stay cold when the CH is flat out.
The lever on the valve moves freely, though back driving the gears by the sound of it. I've removed the actuator from the valve and cycled the programmer to see if the actuator works and the drive rotates to three positions in response. The spindle on the valve rotates freely >360 deg in both directions when turned with the finger and thumb. The manual lever moves back to its set position if moved with the valve opened.
I'm at a bit of a loss for fault finding ideas. The only thing I can imagine is that the actuator can no longer drive the valve to the correct position although it has enough power to turn itself. Does anyone know the correct positions of the manual lever for each position of the valve? At present it only moves to just before the mid point. Should it move almost all the way to the MAN detent for some settings?