Did any particular model years have a higher failure rate than others?
Worked on a G26Q2-75 which was around a very early 90's unit. Had the BCC3 board, and the original honeywell spark box. Much older than the ones with the surelite control. Anyways the heat relay on the board had an open coil, and the main blower would not come on when in heat. It cycled off high limit for who knows how many times.
So in swapping the cooling relay for the heat relay at a component level, everything works until a replacement board can be obtained. Question is, did the primarys get damaged? They were not discolored like the ones in all the pictures on here. I was able to inspect it well. Also the outlet pressure was 3.3" w.c and the temp rise was 53. So it should be well in spec.