Strange Power Supply Behaviour
I have an early 2011 13” Macbook Pro that is exhibiting unusual power issues. On the surface, it seems like a common problem: Mac won’t turn on when magsafe is connected, battery is missing when it turns on, fan runs at full speed, etc. The solution typically is to reset SMC and PRAM. I have done all this and more and this question is about the issues that I have not been able to figure out after three days of researching this problem.
When the magsafe is connected, it goes green immediately and the front sleep led starts blinking periodically. Power button does nothing. I opened the back of the machine and discovered that the fan basically starts spinning when the magsafe is connected, but it does not receive enough power to actually boot up.
The correct SMC reset procedure, cmd+option+shift+ power button does not seem to do anything. However, the old procedure, unplug the charger and hold power button for 10 seconds, connect the charger while continuing to hold the power button for 10 seconds, release, works. The computer boots as soon as I release (I do not need to press power again, it just boots), but now the fan is at max speed, and the battery is not detected at all. I was running Lion, and discovered that El Capitan would fail with installation errors and Sierra would tell me that the power supply needs to be connected (though charger was already connected).
The breakthrough was when I messed around with the battery. After a day of experimentation, I have found that I can consistently boot up with the following procedure:
Press and Hold Power Button to discharge any residual power
Connect Charger - Green light comes on
Wait for the fan to start spinning up automatically (power is never pressed)
When the computer fails to startup and fan starts spinning down, plug the battery in
On next spin up cycle, the machine now will successfully boot.
Fan runs at normal speed.
Battery is detected, but does not charge.
Magsafe remains Green.
Coconut Battery reports that the battery is in good condition.
I managed to update to Sierra without any issues.
Pushing the battery indicator button on the left side leads to a single flashing green light for five seconds.
HOWEVER, about a minute after the machine boots, it CRAWLS. Kernel Task runs constantly and consumes all of the CPU power. Machine runs super cool because of the extreme thermal throttling.
If I shutdown from this condition, the machine again fails to power up and I have to repeat the procedure. However, the fan continues to constantly spin up, meaning the machine is constantly trying to power up unsuccessfully. I left it alone in this state for 30 minutes and discovered the bottom was quite warm, which means certainly a lot of power was being pumped thru the board, even though it was not booting up.
I am unsure what my next diagnostic move is. I figure I need to get another mac to check the battery and the charger first. If those two are cleared, then the problem is hopefully just the DC board, BUT also possibly the mainboard? Beyond the battery and charger, I am not sure what else I can check. Any advice is appreciated.
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