Ideal Isar pump stop circulating and h.e overheats

[willshill]

Hi all

My Isar HE24 had very poor hot water coming out of the taps. So I run the hosr through the heat exchanger and this was clean (only 1 year old) but when i checked the diverter valve, this was all bunged up. So i ordered a new one and but freed up the old one just to get some temperary hot water and heating...which worked. But then shortly after, the capacitor in the pump failed, so i replaced this. By this point the new diverter valve arrived and I fitted this.

I now find that when I switch the mains power on, I hear the pump fire up, i hear the actuator moving and the central heating kicks in. But then shortly after the pump appears to stop (i think) and then shortly after i get the 3 horixontal lines to say the exhanger has over heated.

Any ideas as to what may be causing this and what I can check next?

Much appreciated

 

[willshill]

The heating runs for 1 or 2 minutes then its sounds almost like the water supply to the pump slowly fails. The pump clearly sounds like water is passing through but then it gets slowly quieter. ..