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820-02020 a2338 fan full speed all working good

Y

yair37

Member
Hi, something very weird: there is no water damage or known damage. The Mac is fully functional (charging fine, boots fine, and all parts are working).
I put the board into a different body and it was the same, the fan immediately goes to full speed when I turn it on.
 
Y

yair37

Member
SMC_FAN_PWM get 1v stable, on a good board is 0v probebly or he get the command to turn full speed fan or bad CPU.. where is the temp sensors? i will check them?
 
2informaticos

2informaticos

Administrator
Staff member
"SMC_FAN_PWM get 1v stable"
That is not a DC voltage.
Voltmeter gives you an integrated DC reading according with the width of the pulses.

However the fan can also be controlled by DC voltage there.
You can disconnect SMC_FAN_PWM line from CPU and set a DC voltage, which let fan spins at desired speed.
 
2informaticos

2informaticos

Administrator
Staff member
First of all, it must be from a S0 state; so fan can't spin in suspend mode.

Now looking at fan control circuitry, attacking UE501 with DC voltage is not an option; QE500 works propely with pulses only.
I recommend to check all the components there; post their voltages.
 
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