Help diagnosing CH problem Biasi Riva Compact? Diverter?

[cascas]

Hi,

Can anyone help me out diagnosing a Biasi Riva Compact HE Mk2.

HW works fine.

Rads stop heating except bathroom and bedroom (closest 2 to the boiler). Pump is making sounds as if it is working (stops when unplugged)

Flow is hot, return is cold when CH is running. Boiler cycles keeping flow hot,but return does not get warm.

My though is Diverter Valve, but if this is stuck on the HW position, would the flow get hot on this boiler (assume it is dumping heat into the flow by gravity flow)

On the Biasi does the whole diverter need replacing, or just the actuator?

All leads greatly appreciated

Read more: http://www.ukplumbersforums.co.uk/g...iva-compact-diverter-valve.html#ixzz2E8SgoaG3

 

[bucksplumber]

If the flows getting hot then I would've reluctant to blame the diverter valve as it seems to be moving into position. Can you hear the diverter valve move?

How old is the system? Also have a look in the F&E tank and see what state the waters in? could be a blockage in the pipework. Unlikely that it is but it's worth a check as its been known. A way to check for blockages is to run a magnet over the pipes and if it sticks then its likely to be blocked.

Another check to try, turn off the rads that are getting hot and see what happens to the other rads?