Baxi Central Heating Boiler problems

[Sticky Andy]

Baxi wall mounted central heating boiler WM50/4PF switches itself off/on every couple of minutes.  I have replaced the thermostat, but this hasn't cured the problem.  We have hot water but the radiators are barely warm - pump is working O.K.  Any suggestions?

[Tim Baxter]

Boiler turning on/off every cupla mins means it's up to temperature and probably ok.

Are the hot water and CH fed from same pump? if so, pump is working but you may have blockage in rad feed or return pipe or all rads turned off or all rad thermostats turned down.

How do you know that the pump is working.  Pumps turned on after long off will hum/vibrate and eventually blow fuse/burn out but will not pump as impeller siezed.

If system is old/dirty you may have black iron oxide build up in rads get FERNOX type flushing liquid and fill system with FERNOX type anti-corrosive to prevent it doing it again.

Rads may be full of air, feed and return pipes should be hot, though.  Is your header tank losing water through system leaks?

[paultheplumb]

if you have a 2 port valve or 3 port valve it couuld be stuck in position which is a common fault try opening it manually with the catch on the side which reads man/open