Macbook Pro power issues; Dim charging light, limited power.

Question

So I'm having some serious concerning issues with my 15" MBP while connected to AC power. Recently my AC adapter gave out so I bought a replacement on ebay. While waiting for it to arrive I used a borrowed a 65W charger to charge between uses, which as I understand should not be an issue especially when only charging. At some point the charge light on the 65W began showing only a very dim green. It still worked fine on the Macbook.
Upon receiving my new adapter and plugging it in, I observed the dim light again and decided to try and see what was going on. The system profiler registered a charger present but not charging, but the battery seemed to charge regardless. When using the computer on AC power, battery life would decrease slowly and it would eventually fall into sleep mode when the battery hit zero. Something that seemed to be accelerating from what I imagine to be the battery on its last legs as it had been giving a "Service battery" warning for a few months before this. Eventually the computer began to shut down and attempt to restart immediately on startup with the battery, and operated on AC only, without the battery, as long as I didn't use any applications that demanded high performance from the CPU.
I have tried resetting the PRAM and SMC with no avail.
Well, I just received a new battery in the mail (not that I expect it to fix the main issue), and I'm hesitant to try to charge it.
Basically, what I'm wondering is should I be worried about damaging the new battery with what seems likely to be a damaged charging circuit?
Also, from what I gather, this problem is usually related to the left I/O board where the magsafe and charging circuit is.
Is there any way to determine where the fault is for sure before I go buying replacement parts? My hope right now is that it is in fact the I/O board and not the logic board because of the cost of a new logic board and the fact that I could easily replace the I/O myself.
Any insight at all is greatly appreciated.
Message was edited by: Eiichi133
Message was edited by: Eiichi133

Answer 1

Here's a link for troubleshooting the power adaptor:
http://support.apple.com/kb/TS1713
Also check for any debris in the power port which may be keeping the adaptor from making good contact.
It's always possible the power adaptor from EBay is faulty. You need to try a known good on, like a working one that a friend has or one at the Apple Store.
Is the new battery a genuine Apple battery or a third party battery. Third party batteries can be difficult to get working. I have one from OWC that's like that--it takes its time to begin charging instead of starting to charge in a second or two.
The best way to troubleshoot all this is to try a known good battery and a known good power adaptor. Your new ones are still in unknown condition. If you have a friend with the same Mac who has known good battery and power adaptor, you can try those in your Mac--and yours in the other Mac, and narrow down the possibilities.
If the Mac fails to charge even with a known good battery and power adaptor, there's a good chance that the I/O Board is bad. But I don't know of a definitive test that would tell you for sure.
Good luck!