combi boiler not lighting

[john]

Been trying all morning to get newly installed combi boiler to light. All the pipe-work to domestic hot and cold water is new as is the central-heating pipe-work. I have flushed and refilled the central heating to 1.5 bar as per the manufacture instructions. When the heating is turned on the fan starts, the pump runs and a few moments later the amber light goes on signalling flame failure. I was advised that gas valve has air in it and to try continuously switching on for

20 minuets. This did not work. This boiler is Ravenheat small combi bought in B&Q (White Star). I have checked the gas supply is on. The ignition is electronic.

[geoff]

In message , john writes

Did you switch the gas back on ?

[Ed Sirett]

Take better advice see the FAQ.

This did not work. This boiler is Ravenheat small combi

The obvious first idea closely followed by the second did you turn the gas isolator to the boiler on? Followed by did you purge the gas pipes?

[Tony Bryer]

To insult your wiring abilities, check the polarity of the supply. A lot of flame sensors work by leaking current to earth and if you reverse the supply you get exactly the symptoms you describe. Don't ask me how I know this

[geoff]

In message , Tony Bryer writes

I probably posted it a couple of years ago

[john]

Well I have just found the problem. A chap at work is an electrial engeneer also knows a lot about plunbing previously worked as maintence engeneer in a factory.He suggested the casing may not be airtight. Or something to do with the air sensor not working correctly. When the casing was off I noticed a small red plastic pipe comming from a small unit in the top of the boiler to connect to the inside of the neck of the flue, was twisted, I straigntened this and low and behold when the casing was very carefull put back the boiler light up. This small red pipe may have been moved when the flue was being fitted. This little boiler gives plenty of hot water runs very quietly and was £375 from B&Q. Thank to every one for the suggestions..