i have a old computer here prcessor fan is not running well. after 12/15 mins it's droped

Put a new one on it then!!!

try to clean the dust,, or put some oil on it...make the motor easy to span...

If you use desktop computer then you need clean the dust of the fan. But the best option is buy a new fan.

yeah i am alos having this same problem but my problem is different one. Would anyone know why a CPU fan would stop running. I removed the fan from the heat sink and tested it on a different motherboard. It worked fine. I suspect my current motherboard and maybe some BIOS settings may be disable but I don't know where and what to look for next.

Answer to first problem. Buy a new fan and soon! it sounds suspiciously like you are cooking the Processor! And suck the dust out of the system. Power the system off and use a vaccum cleaner/airduster areosol.

Answer to Hijack above,It's the pins on the board that have failed look for the pin outs marked sysfan on the board, you may find these are still operational. The problem you may encounter from here, is that some systems may not boot as the system cannot detect the fan.

Buy a new fan I thick Noctua is the best manufacture of cpu cooling fans ..

Hi!
I advise you first clean your radiator and fan, and change thermal compound. It can help you, because your PC allready worked well with this fan and problem appeared recently

change the fan oterwise it will harm your computer.and for best cpu fan google it .you will find the best one.

Open your Fan and clear the dust and put it back in and try... if same issue occure then you need to replace your fan.