no pwm in fan pin
I have a 2011 mac mini that has full speed fan all the time. I have checked the fan in other mac mini and it works correctly. I have checked pin 2 (near gnd in the fan connector) and it is always 3.3v, no pwm. I do not know which element generates that pwm for the fan, nor where is that component. I have tried to follow the track that goes out from the connector but i have found nothing. Anyone with the schemes may help me? please. it seems there are no missing components on the board. thank you
Hello, i do not know if my smc chip is broken or not, what i know is that in the fan connector i have 12v in pin 1, tacho is measuring correctly in pin 2, pin 3 is always 3.3v and pin 4 is gnd. The problem is that the pwm that controls the speed of the fan is not existent, pin3 is always at 100% so 3.3V all the time. I do not know what chip generates the correct pwn to control the speed. I tried to follow the track that goes to the pwm but i got lost.
Does anybody have the electric circuit of the pwm? or tell me what chip is the smc? i cannot identify it in the motherboard.
I run the diagnostic and i got ( 4MOT /1/140000003: exhaust-6262) the number after Exhaust is the revolutions of the fan so that means nothing, it is maximum speed. There is no speed control because there is no pwn, just a 3.3v signal.
If could see the electric scheme maybe i can identify if it is the smc chip that is broken or maybe some capacitor or resistance.
Macfan software shows the speed of the fan and all the temperatures, everything is ok but the fan speed that has no control regulation.