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  1. #1
    Macbook Pro 15" Late 2011 (820-2915) fan quarter spin

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    Macbook Pro 15" Late 2011 (820-2915) fan quarter spin
    Hi all,

    I have a 15" Late 2011 Macbook Pro (board 820-2915) and I have the "fan quarter spin problem".
    I've started diagnosing when i found that my R7021 and R7022 resistors don't have any continuity and even if i try to measure the resistance, it doesn't even get close to 10 ohms on neither of them. On the other hand if plug in the charger I have voltage after each one of them...

    Can you guys give me a lead on this one?

    Thanks in advance...

  2. #2
    Macbook Pro 15" Late 2011 (820-2915) fan quarter spin
    pigoo3's Avatar
    Member Since
    May 20, 2008
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    U.S.
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    40,801
    Your Mac's Specs
    2011 17" MBP 2.2ghz, 16gig ram, OS 10.11.6
    Hello tigas...welcome.

    To be very honest...this is the first time I'm hearing about this issue. Given the amount of traffic we have here at Mac-Forums...in the 8 years since 2011 when this MacBook pro model was released...first time (I think) anyone has posted about it (which would lead me to believe the issue is not that common). I also have a 13" and 17" 2011 MacBook Pro...not sure if it's an issue only found with the 15".

    Anyways...I did a bit of research into it...and I see there are at least a handful of videos on the internet (have you checked them out)?

    Apologies for not being more helpful.

    - Nick
    - Too many "beachballs", read this: Beachballs
    - Computer seems slower than it used to? Read this for some slow computer tips: Speedup
    - Almost full hard drive? Some solutions. Out of Space
    - Apple Battery Info. Battery

  3. #3
    Macbook Pro 15" Late 2011 (820-2915) fan quarter spin

    Member Since
    Apr 25, 2019
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    I've already looked at Louis Rossmann videos and checked many others, but I can't find my problem.
    Do you know what rails should i check or what kind of diagnostic should I do?

    Best regards

  4. #4
    Macbook Pro 15" Late 2011 (820-2915) fan quarter spin
    pigoo3's Avatar
    Member Since
    May 20, 2008
    Location
    U.S.
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    40,801
    Your Mac's Specs
    2011 17" MBP 2.2ghz, 16gig ram, OS 10.11.6
    Can you explain what exactly the "fan quarter spin" problem is (yes I know I could Google it).

    The reason why I'm asking is...are you 100% sure this is the issue you have? If the resistors you tested are not displaying the parameters they're supposed to (to indicate the fan quarter spin problem)...then maybe this MacBook Pro has a different issue.

    - Nick
    - Too many "beachballs", read this: Beachballs
    - Computer seems slower than it used to? Read this for some slow computer tips: Speedup
    - Almost full hard drive? Some solutions. Out of Space
    - Apple Battery Info. Battery

  5. #5
    Macbook Pro 15" Late 2011 (820-2915) fan quarter spin

    Member Since
    Apr 25, 2019
    Location
    Portugal
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    4
    From the videos I watched, if you plug your board to the charger, the fans should start spinning non-stop. Mine start spinning and after 1 or 2 secs they stop.
    I started by checking the power rails that should be on when connected to the charger, like PPBUS_G3H and PP3V42_G3H (on this one I have 3.47V, I don’t know if it is a problem or not), and they are there. Then I found something about the “current sensing resistors” where the system uses those to check the current drop and see if there is a problem with the consumption, and if there is a problem it shuts down thus stopping the fans. This is where those resistors belong (R7021 & R7022). I tried to measure the resistance on both and continuity, but no dice. When i plug the charger I have voltage on both sides of them.

    I really need some confirmation on my suspicions ��

  6. #6
    Macbook Pro 15" Late 2011 (820-2915) fan quarter spin
    MacInWin's Avatar
    Member Since
    Jan 01, 2009
    Location
    Winchester, VA
    Posts
    5,853
    Your Mac's Specs
    MBP 15" Mid 2015, iPhone XS, an iMac, plus ATVs, AWatch, MacMini
    You cannot measure the resistance of the resistors whilst in circuit. The reason is that there are multiple paths of resistance--the one directly through the resistor and the ones (all of them) through the rest of the computer. What you end up measuring is the average of the lot, which may vary depending on the charge on all the capacitors and coils along the way. Ditto for continuity.
    Jake

  7. #7
    Macbook Pro 15" Late 2011 (820-2915) fan quarter spin

    Member Since
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    In some cases that rule does not apply, and for sure this is one of them.
    The resistors I am talking about are measured on the following video at 2:14: YouTube

  8. #8
    Macbook Pro 15" Late 2011 (820-2915) fan quarter spin
    MacInWin's Avatar
    Member Since
    Jan 01, 2009
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    Winchester, VA
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    Your Mac's Specs
    MBP 15" Mid 2015, iPhone XS, an iMac, plus ATVs, AWatch, MacMini
    He is not measuring the resistance of the resistor, but of the resistor in parallel to the rest of the circuit, which is what I said. The results he got (10 ohms, 2 ohms) were not for the resistor itself, but the resistor in the circuit. He gets the value of the resistor to put back into the circuit from the circuit diagram that he has access to for his work.
    Jake

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