There are two things two protect against overheat, a thermo fuse in flue that will pop like a breaker to cut power, also a line off one post on the thermo fuse that goes to another thermo fuse, it is a resistor. It is secondary backup. When it goes, cannot reset but have to replace. In my unit the resistor fuse went first. Replaced and working well. Thanks for all the suggestions.
Jim and Silene
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