Hi. We have a Worcester 9.24 Electronic. CH work's fine but when we try to use hot water the boiler never kicked into full action. The flames start very low as when the heating starts to reach set temperature and slowly increases a bit but not enough for proper hot water. The diaphragm is fine as it pushes up all the way onto the micro switches. Could this be a broken micro switch or maybe a bad thermostat? I can work on the boiler fine if I knew what to replace but not very good at diagnosing the fault. Please help.
Thanks.

Lee, December 2007

Hi there the problem sounds like the dhw thermister is at fault, also the burner pressure is adjusted by a pot on the pcb so check this, i think its around 15mb on dhw full rate mode, the value of your thermister should be between 2k ohm and 18k, if its out of these values its knackered, its also possible its inacurate, only a ffew quid, and worth changing as a procaution, the other possibility is that the calorifier/dhw heat exchanger is full of muck, and not transfering the heat, giving the thermister a faulse reading, hope this helps

Steve, March 2009