Baxi Bahama Combi Boiler?

Had a few problems with the boiler a couple of years ago. Replaced the 2 flow switches and it has worked ok since. A while ago however after switching off the HW it would take some time to switch off and every now and again it would need resetting, CH seemed to be fine though. Changed both flow switches today, now HW is ok but CH will not even switch on. Talk about dont fix it if it aint broke. Any ideas ?