Dodgy pump or valve? Help and information on all topics relating to your central heating, air conditioning and ventilation issues.

[nuscw]

Hi all,

Had problems for a while with CH. Initially not switching off despite thermo working OK. Changed the 3 port valve & pump 2 years ago and things have been fine since.
Put the heating back on this year and now it doesn't come on. Have found that if I bang the top of the valve it actuates and the heating comes on OK. Soon as the thermo turns it off again, have to go through the same carry-on to get it back on.
I've kind of assumed this is the valve arm sticking, but there's also a lot of air that seems to be rattling around the system. Planning to desludge and drain, if no better will clean the valve or replace it. Does that sound right to you guys?

Cheers, Stuart.

P.S. Forgive my ignorance, but the CH pump is permanently on - should it not turn off when the heating's off?

[The Heating Doctor]

Yes the pump should switch off how long after the boiler switches off depends on type of system, but no longer than 10-15mins. You do hava a valve problem. Some systems use the valve to switch pump off ie grey & orange wires.