Just installed a new built in cooker,after a few minutes the flames start to lift and it cuts out,with door slightly open it works fine so obviously not getting enough air.The fan on the back seems to be sucking air in rather than blowing it out,not worked on many ovens,should it draw air in or blow it out?The electrics had allready been sorted befor i got there,would reverse polarity cause the fan to rotate the wrong direction therefore causing such a problem?Or is it likely to some kind of blockage internally??