The motorised central heating valve is making a loud clicking noise when it is in the heat water position. Is this an indication that it is getting worn out and do I need to replace it?. It does not do it all of the time but when it does the noise rattles through the heating pipes.
This valve should be silent except for a soft 'whirring' sound when in operation.
I'd guess that the join between valve spindle and motor has become worn or dislodged, this would cause the motor to slip and as there is a cog it operates on this would sound like clicking.
Replace the valve, it is relatively easy as there should be isolation valves before the diverter valve so it should be a matter of unbolting the valve and putting a new one in.
The valve should come with the electric motor matched to it, don't be tempted to replace just the valve as this may prove a false economy.