Quote by benen
It's a 92 kon_tiki swift, it's was the wind, working perfectly today can't spell the name of heater it's the one that is in most vans
Extend the flue on top by 100mm.... ‘eddies’ (air currents disturbed by objects) swirl across the roof causing a temporary higher pressure on the outlet preventing air flow through the heater & making it flame out.... the extended flue takes it above the eddies.
Even a temp one (12” of 150mm drain pipe) set around the existing flue will stop it.
I’ve been there with the same issue.