Released June 2012, Model A1278. Intel processor with Turbo Boost, Up to 512 MB DDR5 Video RAM

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Battery not recognized and fans running really loud.

I have a macbook pro 13" Mid 2012 and I recently replaced the hard drive cable on it, upon startup I noticed that the battery indicator had an X on it and the laptop only works with the charger plugged in and the light on it is always green. My fans are also running pretty loud on start up and it takes a long time to load my profile, and when it does the computer in general is running slow. I already tried an SMC reset, I don't think the SMC reset is successful because the macbook starts up right away when it should not. After the reset you're supposed to press the power button for it to turn on. I've also noticed the LED on the front blinks 5 times before starting up. At one point when I did the SMC reset it did not turned on so I assumed it was successful which it was because the fans were not running on high anymore. But the battery problem still existed and now trying different methods of fixing the battery brought back the fan problem.

The battery indicator doesn't even blink green or light up so I tried unplugging the battery indicator from the logic board but the problem still persists.

I've also put in a friends battery into the laptop and same thing happens so I know it's not a battery problem. Is it most likely the logic board?

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1 Answer

Chosen Solution

You have sent 12V to the SMC by shorting the silver battery pins, above where you disconnect the battery. This has sent 12V to the SMC data line responsible for detecting and communicating with the battery and charging chip, so the MacBook will no longer detect the battery.

The only way to resolve this would be to either replace the logic board, or desolder an SMC from an 820-3115 board, reball it and solder it on your board, since it has programming specific to the year and model of the MacBook. This is definitely not an easy task for a beginner, so I would recommend either replacing the board or sending it to a repair shop who is able to do this.

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That or you knocked off something by mistake... And you're sure there is no liquid damage along the edge of the logic board where the LCD connector is attached?


yep 5 blinks means battery not detected - if another battery does the same thing (and that battery charges in another MacBook it's something to do with a component on the logic board!


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