Vaillant VCW-Sine18 T3WFH Lights but then goes off after 5 Min?

My boiler lights easily but after 5 minutes there is a click and then it goes off and the pilot goes out.
Martin, January 2019


done
Blocked pilot or a new thermocouple would be the obvious answer.
If the pilot is weak, it can be dragged away from the thermocouple by the main flame

Carefree, June 2019
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