Pump keeps turning on and off when hot water selected

[happypig]

Had an issue the other day where the boiler had locked out. reset it and turned HW on manually. After a while I noticed that the boiler/pump was doing the following :
pump runs for a couple of seconds
boiler clicks a couple of times
pump stops.
Repeat every 10 seconds or so.

Checking the pipes to the cylinder, the feed and return seem to be hot and the cylinder is hot; I *think* it's only doing it when the hot water has heated up.

Just wondered if anyone has come across this before and could give some pointers ?

 

[Dan Robinson]

Care to give us any useful information?

 

[happypig]

which informations require you ?

 

[Dan Robinson]

Boiler and control configuration would help.

Read the FAQ and post back.

 

[happypig]

Ah, right, ta.

It's a closed system. Hot water and heating can be activated independantly. Boiler is potterton. there is a single valve above the pump sending water to the CH via a 22mm pipe and to the cylinder via a 15mm pipe.