Potterton puma 100 e that goes to lockout as it wont fire with the case on. remove case and burner inspection cover and it fires. I have a van load of spares so have changed the gas valve, air pressure switch, spark electrodes and full sequence and modulation boards, i have checked the vertical flue,fins on exchanger, fan ok, tubes all ok, im lost as what to do next-other than change it!

mark winfield, November 2005

u must b getting flue gasses in the air intake the inner flue isnt sealed properly leaking into the air intake .

andy the fitter, December 2005