ariston boiler problem

[maxmark]

hello i wonder if someone can help i have a ariston eurocombi mffice 20 type c i,ve been having problems with it staying on for longer than 1 minute then it cuts out and restarts again and so on i,ve checked all thermastats they are ok then i removed sealed panel to checkoperation of fan turned it on and it all worked ok no problems with panel off put sealed panel back on and problem came back took off panel again just to check if it worked ok with it off and it did could you give me any tips thanks mark

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[corgiman]

Air flow switch probably or a blockage in the tubes to and from it