heatline vizo 24 plus heating not working?

i have a problem with my heatline
when i switch on my heating it will run for about
10 minutes and then it will switch over to d.h.water indicator witout turning on the the hot water tap
and the heating indicator will switch off and the heating will co cold but the boiler will still run
and the d.h.water will keep heating up witout turning
the tap on i replaced the flow sensor no joy could
it be the pressure switch please reply a.s.a.p thank you