worcester greenstar 35cdi overheating

[hheng]

Hi fellas just wondered if any of you clever chaps have a clue what is going on with my combi boiler? Worked fine for about a year or so (we moved in november last year) but for the last few days whenever i turn the heating on the temperature rockets to over 100 . The rads are cold as the pump doesnt start running. Just heats up the water in the boiler itself. Had the front of the pump off and its not seized i.e its moving freely when turned with a screwdriver. Hot water works fine and the heat exchanger is clean. Rads are all vented and pressure in the boiler is ok so im thinking maybe a sensor or something? Possibly pcb? Any advice is greatly appreciated and i hope ive given enough info here.
Also i should note that the boiler displays no error codes just powers down when gets too hot
Thanks again
Hheng

 

[ianmcd]

Sounds like the diverter valve motor may be stuck in the HW position, this will stop any water being circulated to the radiators, it could be the motor itself or the flow turbine telling it that water is being drawn best to get someone in Im afraid, you may want to consider Worcesters own fixed price repair but at £270 a decent fault finding Engineer with experience of your boiler should be a lot cheaper

 

[hheng]

Thanks for replying ian. The diverter moves open and shut ive seen it moving. Weirdly im tinkering around with the boiler and resetting etc (im pipefitter/welder so im vaguely aware) and the thing has fired up as normal and running at steady 75 degrees. Im not too hopeful about next time it fires up though! Is this a sign something is on the way out would you say? Thanks for you time buddy

 

[ianmcd]

Sounds like you have a blockage somewhere then mate, your boiler is a decent piece of kit and they dont usually give many problems, if the motor is moving are you sure the rest of the diverter section is moving too ? shouldnt be too hard to find where the flow stops