Halstead Ace combi boiler problems, HELP!

[august73]

Problems with this problem started about a year ago just before Christmas ( not the best time) bUt likely I had a british gas insurance 100, fixed next day no problem. 2 weeks later the same problem, again plumber fixed this. Since that time we had about 6 visits from british gas plumbers and what they only managed to fix was my monthly payment from £15 to £28!
then i just gave-up! Problem i got is that when you switch the central heating on boiler starts but few second later stops and green light 'power on' starts flushing for some reason.
in order to get your heating on again I just need to turn the hot water tap on for about 10 seconds, boiler starts heating hot water, then just turn the hot water tap off and central heating starts without any problems. but when it switch off I need to do it again, turn the hot water tap on and off.
Please help me with this

 

[Gasguru]

The primary flow switch is not operating. Drop down the controls panel and check the pin (on top of the right hand brass manifold...purple wires) pops up when the pump starts for heating or hot water. Would appear to be a flow restriction issue....not always that easy to fix.