Halstead ace combi ( hot water no heating )

[barty63]

Hi all some advise please... halstead combi works fine on hot water no problems, but when central heating on it fires for 30 seconds the flow pipe gets hot and the flow pipes on rads get hot, after 30 seconds the boiler cuts out but no flashing lights after 5 mins boiler will light again and so on, return pipe on boiler do not get hot, pump is running, seems like a block some where, been told by halstead its the thermister ( ch ) but has been changed makes no difference........... any ideas please.

 

[Toned.f]

Sounds like divertor valve.

 

[barty63]

just been told that the return pipe that enters the boiler where the water housing is just below the pump has a filter and could be blocked is this true, return pipe to the pump is cold but the pump is running but very hot, can this filter restrict the flow back into the boiler.......

 

[5544]

what are the flow anfd return temperatures like. does sound like a flow problem.