potterton kingfisher mf70 will no turn of

[winterwood43]

hi hope someone can help kingfisher mf 70 will not turn off when i turned the power to boiler on yesterday it fired up without the timer or thermostat set to run the only way to stop it is turn boiler thermostat to zero if allowed run to the rads get very hot any ideas

 

[oldbuffer]

1. Probably a microswitch jammed in one of the motorised valves / the three port valve.
2. Proper diagnosis requires a multi-meter and the knowledge and experience of how to use with mains voltages.
3. Try moving the "manual" lever on the valve(s) and see if it makes a difference. With the room thermostat and cylinder thermostat "off" should be stiff to move. If floppy, may be stuck at "open".

 

[Deleted member 267285]

+1 for failed motorised valve head/microswitch

 

[winterwood43]

thanks will have look tomorrow