lenovo y520 fan2 always full speed problem

[swammyw]

i had broken (no power) lenovo y520-15ikbn mboard: nm-b191

i changed ec sio chip and laptop started working exept fan2 is always full speed
i noticed after i soldered ec sio chip that fan2 pins: +5VS_FAN2 and EC_FAN2_SPEED was bended together, so i thought ec sio chip was damaged and i changed another one ec chip but same behavior occurs, also tried with another fan assembly (i have 2x y520 laptops) but still same story, what controls the fan speed if it is not the ec sio chip, i tried to figure it out from schematics but no luck, i hope somebody can help me with this thanks

[mon2]

Re: lenovo y520 fan2 always full speed problem

On the fan connector should be a PWM signal. This PWM pulse stream defines the speed. It is also possible that a temp sensor is not working and causing the fan speed to be high. What does the bios report for temps? Are they high or normal readings?

[swammyw]

Re: lenovo y520 fan2 always full speed problem

temps are around normal idle temps when i monitored them, lenovo diagnostics shows fans diagnostics not available?, could it be that pwm or speed pin from sio is badly soldered on board?

[mon2]

Re: lenovo y520 fan2 always full speed problem

On PWM, if the voltage is the max (ie. ~3v3) then the fan will be @ max speed.

Respectively, measure the voltage to ground on the PWM pin - even better if you have a scope to monitor if there is a pulse stream on this pin or is it a static voltage level.

Can you link or post a schematic for this logic board?

Will check my database in the meantime. Found far too many iterations of this model. Which one is yours?

[swammyw]

Re: lenovo y520 fan2 always full speed problem

btw pins were bent together from the fan connector, could that have been destroyed the original sio

[mon2]

Re: lenovo y520 fan2 always full speed problem

Yes, it is possible. The PWM (pin #3) is an OUTPUT from the SIO.

The TACH (pin #2) is the voltage OUTPUT from the fan as it spins.

Two outputs bashing each other never ends well. Proceed to measure the PWM voltage from the SIO with the fan installed.

Also check the TACH voltage from the fan itself.

BTW - Is FAN #1 working ok ?

Post a picture of the fan connector so we can review the wires.

You may be able to swap the FAN #2 wires onto the FAN #1 SIO pins for testing of FAN #2. That is, can the SIO pins for FAN #1 control the fan OK ?

[Sephir0th]

Re: lenovo y520 fan2 always full speed problem

Worth to check whether the load switch U56 is internal shorted between Pins 1/2 and 13/14. I'm dealing with this kind of fault from time to time.

[swammyw]

Re: lenovo y520 fan2 always full speed problem

yes, fan1 is working fine

[swammyw]

Re: lenovo y520 fan2 always full speed problem

got fan 2 working, ec fan 2 pwm pin was not sodered properly to mboard