I have an APPHA CB24X COMBI BOILER. My boiler starts working ok, but after a while it switches itself off. and a yellow light flashes every few seconds. Then it starts working ok, then goes off again !! The manual says the yellow light indicates a temperature sensor fault. I had this problem when under warranty and it took the engineers 3 visits to sort the problem out. Eventually they changed the flow switch and thet solved the problem. I have changed the flow switch myself and it has not made much difference. I spoke to a plumber and has said it may be the thermistor or overheat sensor or termostat. I seems the boiler works ok then cuts out. This cut out is the same for hot water or heat. Also I have recently found out that the pressure seems to drop on boiler and I have to keep topping it up, but i cannot see any signs of a water leak - Any Idea's would help please !!

D.Collins, February 2009

how bizarre - experienced exactly the same problems until it finally packed up completely on Sun!! Both the red & yellow light are flashing together. Guy checked it out tonight and said same thing - thermistor if not PCB. Pump is working, Fan is runing but no electric current getting to it, apparently it works in a sequence so because not gettng further than the thermistor and no current at fan, he believes thermistor first place to start, if not the then more pricey job of PCB.

SARAH, February 2009