When I first found out about the bolt issue, purchased a T30 wrench and checked them myself. It's been awhile so decided to check them again this morning. Took 5 minutes. This is how I did it. Open the hood all the way to the windshield for max room to work. Use a towel to protect hood. Put a...
Or my '60 chevy pickup with a column shift. Every time I tried to shift quickly that "three on the tree" would hang up between 1st and 2nd and require stopping and getting under the hood to reposition the worn out linkage. :facepalm:
Make sure you remove that tape that is holding the door safety switch closed. You don't want to mix combustion air with recirculating air. Good job on fixing it yourself. So sad that a "tech" threw parts at your furnace instead of diagnosing it. That was an easy one for a real tech.
Looking at your video, the time delay between when the burners ignite and the circulating air blower comes on is longer than it should be. A high limit is then turning off the burners and it goes into a cool down mode. That on and off is the timing circuit malfunctioning. A bad circuit board is...