Chosen Solution
Long story short. I seem to have fixed some problems regarding malfunctioning thermal sensors on the logic board. However, I have some new obstacles that have popped up. After reassembling all the parts (including the battery), I tried turning on the laptop, but it would not respond. No sound, chimes or display. This has happened before just a couple of days back but I fixed it after performing a power cycle. This time though, the power cycle didn’t fix the computer turning on with the battery connected. I wrote this post with the MBP booted and working, without the battery, so there’s nothing wrong with the logic board. Or is it? The moment I connect the battery, it would die again. And btw, the battery is at normal condition, connecting the charger shows proper lights and the battery indicator is working. I’ve tried the SMC reset and a number of key combinations, but it would simply not turn on with the battery (works without it). Any suggestions?! Update Laptop finally working. SMC reset without the battery could have solved it. Booted up without charger connected.
the battery function is controlled by the SMC chip on the logic board. If you are 100% certain the battery is working (ideally you’d be able to test it in a different machine to confirm this), then the logic board is at fault unfortunately. While working on the machine, were any of the chips around the battery socket knocked or damaged? even a tiny capacitor can make a difference. Also, was the machine a liquid spill originally? I’d suggest running it will all non-essential boot items disconnected, this includes things like the airport/BT board, isight, trackpad, battery indicator board, etc. see how well it responds after that. But i have seen a battery and a logic cause these symptoms before, so it really could be either, but more likely logic in this case, as it crashes when connected.
