How can my boiler be fixed i main Medway 55/54 ?

Probably the flame failure thermocouple has failed.
I did a quick search and found what appear to be at least 2 versions of the manual for this.

Page 18 of this one looks useful

http://www.acwilgar.co.uk/Boiler-Manual-PDF/Baxi/BAXI%20MAIN%20MEDWAY%20SUPER%20GCNo.52-476-39.pdf

This is the one from the Main website:, which isn't so forthcoming about the thermocouple:

http://www.mainheating.co.uk/docs/101209_Main_MULTIPOINT_BF_Guide.pdf

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November 2016