Worcester 30 Combi is mk3 over heating

[Rob12345]

Hi, hoping someone can help, I have a Worcester 30 si green star mk3 if you turn the tap on full the hot water goes luke warm if you turn the tap down so the flow is slower the boiler overheats and the boiler shuts down and you have to reset it heating works fine, I’ve changed the heat exchanger hw sensor and the flow turbine adaptor that was broken and still cutting out.
Thanks for reading my post, Regards, Rob

 

[cross thread]

Plate heat exchanger restricted

 

[Rob12345]

Hi, could the new heat exchanger be faulty then

 

[cross thread]

Have you replaced the main heat ex or plate ? Was it new

 

[Stadan20]

If it overheats it's a main hex issue circulation/choked up flame side