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MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

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    #41
    Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

    So I did cleaning of the area above and now machine fans turn on for one second and then turn off, like quarter fan spin.

    I will replace BIOS chip

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      #42
      Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

      I replaced BIOS chip, issue remains.

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        #43
        Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

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          #44
          Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

          Can anyone help?

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            #45
            Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

            Can anyone advise further?

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              #46
              Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

              Hi @mon2, can you help?

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                #47
                Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

                Hi. See attached.

                Remove all power. Meter in resistance mode.

                Use the lowest scale on your meter.

                Confirm the resistance from the topside of R7020 current sense resistor to the current sense pin CHGR_CSI_P (pin # 28).

                So you are measuring from CHGR_CSI_R_P --> pin #28 of U7000.

                What is the resistance in ohms ?

                Repeat for the other side of the current sense resistor R7020 and CHGR_CSI_N (pin # 27).

                So you are measuring from CHGR_CSI_R_N --> pin #27 of U7000.

                For each, measure right at the pin on the U7000 IC - we want to be 100% sure the traces are reaching the current sense resistor legs.
                Attached Files

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                  #48
                  Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

                  Hi mon2,

                  CHGR_CSI_R_P --> pin #28 of U7000: 00.5 on 200 mode

                  CHGR_CSI_R_N --> pin #27 of U7000: 00.6 on 200 mode

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                    #49
                    Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

                    Do you have a lower meter scale on your multimeter ?

                    If not, short the 2 meter leads and post your measurement.

                    Then, again with no power, measure the resistance betwee then the pins of resistor @ R7021. What is the reading ?

                    Then again for R7022.

                    Each must be 10 ohms else something is wrong. These resistor values are critical.

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                      #50
                      Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

                      Hi mon2,

                      No this is lowest scale!

                      00.6 by shorting, on 200 mode.

                      R7021: 10.6

                      R7022: 10.6

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                        #51
                        Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

                        Ok. The resistor readings are good on their own.

                        Now check again from one side of the resistor to the actual chip pin. No power in resistance checks.

                        If you still read 0.6 then you are on the wrong side of the resistor.

                        Check the OTHER side of the 10.6 ohm resistor(s) to the IC.

                        What are the readings ?

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                          #52
                          Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

                          Hi mon2,

                          Showing 0.6 on one side and 20 on other. See photo, this is where I measured 20:

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                            #53
                            Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

                            See attached.

                            Measure from the 2 arrow heads as shown for the first check.

                            Reading ?

                            Then repeat for the 2nd resistor check.

                            Reading ?
                            Attached Files

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                              #54
                              Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

                              1: 07.8
                              2: 08.0

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                                #55
                                Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

                                Weird - yet you have proper readings up above across each resistor ?

                                R7021: 10.6
                                R7022: 10.6

                                Check again for the resistors only and then trace the side from the resistor pad to the IC pad. This should be 0 ohms for each leg. Otherwise you have a PCB trace that is faulty.

                                Zoom out with your microscope and share another pic with the R7021 & R7022 resistors. You have a PCB trace fault here somewhere.

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                                  #56
                                  Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

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                                    #57
                                    Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

                                    Across each resistor now measuring 06.2 on both

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                                      #58
                                      Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

                                      Remove one of these resistors and check the resistance out of the circuit.

                                      Each should be very close to 10 ohms.

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                                        #59
                                        Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

                                        Showing 10.3 out of circuit.

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                                          #60
                                          Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

                                          What I do not understand is now out of circuit, I measure other one still in circuit and also showing 10.3! Multimeter misread?

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