Have a cooker that was wired in by a supposedly professional sparky. It is 3 phase, which is the norm here in Germany. The cooker has never functioned properly since being wired in! ie. only the rings and the fan heat work. It worked perfectly before moving into the new home (not mine!). My question is this....all the wires seem to be correct on looking and am wondering if the two black wires could have anything to do with this? Reason being, that without a multi meter etc, I expect that they could be the wrong way round? Any help much appreciated!