Cpu fan off

[d2006h]

Hello,
when I turn my Imac on, the cpu fan do not start. I have removed the cover. all three dignostic leds are on and the over heat led is of. the other two fans are on and the dvd-drive is working too. but no any thing shown on lcd. the cpu fan still off. what is the wrong?

 

[das_stig]

Dead fan, it does happen or the connection is faulty, do you have another fan you can plug in to test?