Truma B10 gas fired boiler not staying lit

[chrisappleby]

My Truma B10 gas-fired water boiler is not staying lit.
I've had it apart and can see the gas burner, flame detector probe and twin-pronged ignitor.
When I turn the controller knob on, the ignitor mechanism clicks continually, gas comes on all the way around the burner, flame touches the flame detector probe, clicking continues then flames go out and red light comes on by controller knob and clicking stops.
I've continuity tested the flame detector and there's no continuity so I suspect it may be faulty.
Any other ideas?
Thanks

 

[The Coops]

Thermocoupling?

 

[chrisappleby]

I thought thermacouple too at first but looking into it I don't think there is an actual thermacouple as such, there's just the probe official called the "flame detector". I don't know if a working one of these would have continuity or not. Mine does not when I test it with a multimeter.

 

[Spriddler]

I thought thermacouple too at first but looking into it I don't think there is an actual thermacouple as such, there's just the probe official called the "flame detector". I don't know if a working one of these would have continuity or not. Mine does not when I test it with a multimeter.

I think you'll only get a reading if the flame detector is in a flame, that's why it's there. If the gas flame extinguishes the detector will cool and go open circuit triggering the closing of the gas flow valve.

 

[Headrush]

Have you removed the cover from the external vent? I know my truma will not light if the vent is still covered, and even then it takes a few attempts with a few minutes gap in between each attempt.

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[SandraL]

Searching for

Truma flame rectification electrode

throws up a few results, not sure if thats what you need though. Works differently from a normal thermocouple that detects heat.
I think, not sure, that the flame rectifies a small ac voltage, if the resulting dc voltage is there then theres a flame.

Waiting to be corrected or/and a better explanation.

 

[chrisappleby]

Thanks for the replies. The vent cover is removed and no spiders webs or other blockages in there.
Will have to try testing voltage when flame is on.

 

[mitzimad]

You need to test for milliamp as its flame rectification