The fault is caused by the spark electrodes. There was a fault in the original design of the spark electrodes. The were designed to be in two parallel lines, and the spark fires between them. However, when the electrodes got hot, they migrated close together, leaving no room between for a flame to light. This causes the boiler to fail to light, and so the error code E133 appears.
The engineer who fixed our boiler replaced the spark electrodes with a new design. Rather than lighting the flame from a spark between two parallel elecrodes, it lights from a spark which fires from one that is L shaped and the other that is l shaped, in a top to bottom way instead of a side to side way. If these electrodes migrate during hot conditions, there is no problem as there will always be a gap between the electrodes with this design.
Hope that was helpful.
The engineer who fixed our boiler replaced the spark electrodes with a new design. Rather than lighting the flame from a spark between two parallel elecrodes, it lights from a spark which fires from one that is L shaped and the other that is l shaped, in a top to bottom way instead of a side to side way. If these electrodes migrate during hot conditions, there is no problem as there will always be a gap between the electrodes with this design.
Hope that was helpful.
