I got it from ebay - steven7679 of UK Heating Spares Limited, Steven says "if you are a corgi registered or gas safe engineer and are looking at buying multiple items or interested in buying from us on a regular basis then please consider contacting us prior to purchase to open a cash sale account, we can often offer discounts on many items or offer direct postage to your customer (invoice will be sent to you not the customer). We only offer trade discount after the first sale"
It is time to look at the blockage in the secondary heat exchanger. If you have lot of muck in the system then the sec heat exchanger gets blocked and this causes the over heat temp sensor to trip and hence red light. follow the instructions to remove exchanger and clean under water by tapping with a plastic mallet or something soft. They are very easy to take out just 2 screws hold them in place.
I had this problem today and I tested each component the over heat thermostat, the flue thermostat, the temperature sensor and the condensate sensor. All were healthy. Cleaned the secondary heat exchanger. None of cured the problem. Moved the wire of the ignitor and the wire which goes from condensate sensor to PCB, and what a pleasent surprise the boiler fired with no problems. So I suspect a loose wire either ignitor white shielded or condensate white shielded wire was the cause of the flame failure.If you need help you may email me on [email protected]
An intermittent fault where the flame would fail occasionally (well more often than not...) and there would be no hot water. It turned out to be the Flue sensor switch. (This switch makes sure the extractor is working before the burner ignites) The gasman changed every other component.. which was quite costly and not very reassuring about his ability - However, all is sorted now. The new flue switch is a slightly different design which does beg the question, was there a fault in the original design?