Had no central heating but hot water ok, boiler shuts down after 2 mins, found (eventualy) that the thermocouple top left U/S. Now have heating and hot water however an intermittent fault remains.
Overheat clicks out(red button at front) this happens usually when running a lot of hot water (bath) with the heating also on.
My conclusion, is either it is getting a message to hot, or the button itself is faulty? Noticed two wires going to another thermocouple? at the bottom of the heat exchanger could this be the issue? diverter valve seems ok. Lever moved to winter setting (is this some form of restrictor) pump ok set on highest flow?. Is there any "haynes type manual available". Thanks for any help.
Regards Roger.

Roger Rowland, October 2007

Thanks for that, the thermocouple could be thyristor as I can,t remember the name from my electrical training some time ago. Anyway it is a device that changes resistance with temperature. I have had two Corgi registered experts attend, one diagnosed the pressure vessel, the other the pump. One did say that the boiler was obsolete and that he could fit a 42cdi for £2900, as they are £1300 (not trade) that makes £1600 for two days work. As a qualified engineer frankly I am not about to pay this, he needs to find a little old lady!!

Roger Rowland, October 2007

there are no thermocouples top left or otherwise on this boiler.
you are breaking the law. get ancorgi boiler engineer in. dont use your boiler until you have because it sounds dangerous to me.

mrgas, October 2007