Noticed on my AC heater box there is an electrical prong broken off, on the right center of the small brown rectangular connector panel. I was looking at a picture of a restored AC heater box and the same prong was broken off. Now I'm wondering if a prong is supposed to be there or if that is how it should be (missing).
Compare it to your connector & wiring diagrams. Seems like it is supposed to be short?
No idea where the connector is now. But I did take pictures when I took it out. Looks like the connector is made for only two prongs and not the third one. So question answered. Man I love having reference pictures!