Heating pump does not switch off

[AlCoops]

I have a mechanical Landis & Gyr timer for a fully pumped system , with motorised valves for water and heat . On occasions the pump still runs despite the timer switching heating and water off. The system is fine during normal operation. It's just that the pump runs unnecessarily. Is this likely to be a fault within the timer that gives the visual impression that it is off (CH and HW lights off) but it isn't really?

 

[CH4]

Your boiler may have a pump-overrun thermostat that is sticking in the 'permanent live' position.

 

[AlCoops]

As far as I'm aware there is no pump overrun thermostat on the boiler. Or is it on the circuit board? Are there any checks I can do to eliminate the boiler or external controls ?

 

[kevplumb]

what boiler

 

[AlCoops]

Ideal FF260 , I've just checked with Ideal and they say there is no pump-overrun thermostat on this model