vokera Mynute 28 SE boiler

[Edin05]

We have a vokera Mynute 28 96 SE boiler and when the heating is switched on only the boiler makes a loud rattling sound. The pressure remains at a constant 1.5bar however when the pilot light comes on the pressure gauge starts to flicker and then when the pilot light switches off (after only a few mins) the boiler rattles and the pressure gauge stabilises.

When the water is switched on at the same time as the heating the boiler does not rattle.
boiler

 

[glasgowgas]

check operation of pump

 

[Agile]

When the water is switched on at the same time as the heating the boiler does not rattle.
boiler

Based on that I would take the view that the pump is working but there is a blockage in the heating circuit ( or all valves are turned off ).

Did this suddenly start or did it come about slowly?

Do you have one or two motor valves? If two what make?

Tony