[SOLVED] Motherboard caught fire and now the system fan isn't working and the BIOS isn't showing up ?

Jun 4, 2021
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I was thinking of installing a new fan in my computer. I was checking what sort of connections my computer has and I noticed that my system fan is only a 3 pin even though my motherboard has a 4pin slot. I was checking out my PSU and I noticed that it has 3 molex slots and a 4pin input. Not an output! I thought this was kind of weird so I tried plugging it into the 4pin slot where my 3pin system fan was plugged in...while my computer was running. I know, it was stupid. I wasn't thinking and I made a mistake. There was a spark and the little chip thing next to the 4pin caught fire (you can see where it caught fire is kind of fried now.
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Thankfully it went out quickly enough. My computer is still working. The issue is that the 4pin system fan slot on my motherboard isn't working at all now and the bios screen isn't showing up. If I spam f12 and f11 I can still go to setup, so I don't think it's too big of an issue, though it is a bit concerning. My system fan is now connected directly to my PSU by molex. It's kind of loud now. I might buy a quieter molex fan. I guess I should be glad my computer is still working all things considered.

So given the situation, I have two questions:

1: Is my computer going to be OK or is my motherboard living on borrowed time? Like it seems to be working, so that should be good enough right?
2: What is the 4pin on my PSU for?!

Thanks
 
Solution
That 4 pin berg connector is a legacy plug meant to power floppy drives. It most definitely is NOT designed to plug into your motherboards fan header, nor is it an input.

It would be hard to say if this would have any big impact on reliability, however I would imagine the system should continue to function in its current state for awhile.

For future note, you can use 3 pin fans on a motherboards 4 pin port. Just line up the notch and plug the 3 pin into the 4 pin port. It will work fine.
That 4 pin berg connector is a legacy plug meant to power floppy drives. It most definitely is NOT designed to plug into your motherboards fan header, nor is it an input.

It would be hard to say if this would have any big impact on reliability, however I would imagine the system should continue to function in its current state for awhile.

For future note, you can use 3 pin fans on a motherboards 4 pin port. Just line up the notch and plug the 3 pin into the 4 pin port. It will work fine.
 
Solution
It happens. When I built my first pc I had a molex to fan adapter included with the case. Somehow, I managed to connect the fan to the PSU AND the motherboard at the same time.

Luckily, the PSU tripped protections and would not power on the computer, so nothing was damaged.
 

iPeekYou

Distinguished
Jul 7, 2014
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18,790
Yeah, what happens after shorting components is really random. OP's lucky it didn't kill anything major. Did some stupid stuff myself, but got lucky and nothing crucial was damaged (so far). Tally count: 1 dead fan, and 1 dead motherboard USB header.