On Saturday, December 21, 2013 1:39:21 PM UTC-5, micky wrote:

The transformer seems to fail when it's hot, but it wasn't hot when I

measured the resistance of the windings.


There are two types of transformer controls: interrupted and intermittent. If you have an interrupted control, the transformer is actually shut off some time after the flame is established. This prolongs the life of the ignition transformer and points to almost a decade. Intermittent means the transformer runs the entire time the burner does, so the trans and points are being used even after they are no longer required.

Someone already mentioned that coils can fail when hot, and burner transformers are no exception. And btw, when they're right, they will fire a gap well over half inch if the points are shaped properly.

If you live in the States, home stores such as Home Despot carry "ignitors", which are drop in replacement for the old style transformer. They mount and are wired in the same manner, but use a high freq switch mode arrangement. They are less than $40, so it's a good idea to have one at home as these things are generally timed to fail nights, weekends, and holidays.