Worcester Combi boiler - HW=OK no CH

[TKD]

The boiler is igniting and giving hot water on demand fine, however the central heating is working intermitantly on either timed or manual??? The boiler iginites then goes out after about 15 mins and dosn't reignite??? You can hear the pump running and a strange clicking noise???? This clicking noise can be made to stop or start by gently tapping the outside of the boiler?? This sometimes causes the boiler to ignite??????????
Anybody any ideas??????????

 

[oilman]

WHICH WORCESTER COMBI? THEY MAKE LOTS!!!!!

 

[TKD]

ITS A WORCESTER 9.24 ELECTRONIC, I'VE HAD A BRITISH GAS MAN OUT CONCERNING THIS PROBLEM AND HE HAS FITTED A NEW TIMER CONTROL BUT THE PROBLEM PERSISTS AND IS STILL intermittent, HOWEVER WHEN THE GAS MAN WAS HERE IT WAS WORKING OK!!!!!
hAVE YOU ANY SUGGESTIONS OF WHAT THE PROBLEM MAYBE DUE TOO SO I CAN POINT THE GAS MAN IN THE RIGHT DIRECTION?????

 

[breezer]

please dont SHOUT