Temperatures and fanspeeds

Discussion in 'MacBook Air' started by greenleader, Dec 23, 2015.

  1. greenleader macrumors newbie


    Dec 23, 2015
    Hello Guys

    I had a water spills on my my MBA 11 and since cleaning the board etc. its in near working condition.

    Two problems remain:

    1. Power button does not seem to work, no biggie as I can get it to boot by plugging in the power cable and it automatically comes on. I have looked for shorting but cannot find it.

    2. The fan will come on halfway though boot up at 6500RPM and stay that high! Using MacFan Control I can see the temperatures of about 34 - 40 degrees (CPU sensor) and the fan is still on 6500RPM.

    I suspect the SMC controller is dead or damaged, certainty the Mac diagnostic tool suggests that its faulty. On occasions it will boot fine and run nearly silent at 34 degrees.

    Maybe I need to use one of the other sensors to get the fan under control?

    Does anyone know or can provide a guide to sensible fan speeds for certain temperatures so I can turn down the fans and still be safe!?

    Many Thanks.
  2. SmOgER macrumors 6502a

    Jun 2, 2014
    Well first of all it should not boot by plugging the power cable so clearly there is something wrong if it doesn't stay off while charging. As it is with water damages, those issues can develop into substantially bigger ones over time.

    That being said, the stock fan profile is tied to one of those sensors that are outside of the CPU. This means that the fan response is slow (but on the upside and most importantly - you get consistent fan speed without those annoying spins up that you would have on a windows machine), in other words, if you rapidly load CPU to 100% from idle, the fan would start to ramp up only when the CPU reaches 85C or so. But if the load is lower or progressively increasing, the fan would speed up at ~75C core temp.

    For the record, throttling point is ~100C, and shut down temp ~110C.

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