I'm still thinking the temperature sensor for the fans. It was discounted quickly. The sensor had a battery lug for mounting. I would think that would be positive It could have been pinched between the wood and the the post. I would guess that post is about 9 to 12V negative potential from the more positive fan lug. Just a small pinch would be enough. You don't need the spark to carry enough heat to melt the battery. It just needs some glowing embers on the wood.
The fans were running. This could have been the perfect fire starter with a 9V battery. Only the owner could know where the wire was, how the fans could have drawn the fire/flame. Maybe there's pictures during the disassembly. We are asking a lot for him to remember where the wires were, how the smoke was billowing up past the wood, His house was on fire. I can't even remember where I put my multimeter 15 minutes ago.
The fans were running. This could have been the perfect fire starter with a 9V battery. Only the owner could know where the wire was, how the fans could have drawn the fire/flame. Maybe there's pictures during the disassembly. We are asking a lot for him to remember where the wires were, how the smoke was billowing up past the wood, His house was on fire. I can't even remember where I put my multimeter 15 minutes ago.