[SOLVED]512 chassis fan not detected

When i was cleaning my pc i opened 2 cooling fans and cleaned them and plugged them properly , but my pc showing 512 chassis fan not detected.
Answer #1
Not plugged in right..or broken wire.
Fan plug should have 3 or 4 holes that line up with the pins on the motherboard.
If the speed sensing wire (often yellow or white) has not a good connection or got broke (at the plug end or the fan end), then mobo won’t detect fan..
(even though fan may still run).
Answer #2
If i don’t fix it will it create a problem?
Answer #3
Don’t really need case fans, throw them out.
Answer #4
If it still works, just ignore the message.
Answer #5
yeah its working fine but getting that error message. Thanks guys