The galaxy s3 is notorious for the design of the charge port allowing the contact pins to break their solder joints to the board.
The big reason I'm replying to this super old thread is this. I have repaired more of these phones than I can count and something that I see over and over is people doing further damage to their device by rigging it up instead of fixing it. Here is what happens...
A couple of the pins crack or break making an intermittent connection with the board, at this point, the charger will still work but you notice some issues occasionally. You likely buy a new charger to see if that fixes it. A few weeks later you notice the problem has gotten worse so you do some work with google and find instruction to wiggle it, jam stuff up into it, pull the charger off to one side, etc. What is going on in the phone at this point is the cracked joints have gotten worse, trying to make the phone charge there have been more connections damaged or the already damaged ones are further damaged. A few weeks later, you have a hard time keeping the phone with enough juice to turn on and finally break down and carry it in to me for repair. The problem is, the constant wiggling of the connector will pull the traces off the board making my job harder and your repair more expensive. I've even seen one or two that could not be repaired. I've seen dozens that required some "creative work" to get patched back up because the device is damaged at the board level. For those not familiar, you cannot simply swap out the logic board. its the brains of the phone and the most expensive part. THAT is what you are risking by not correctly repairing this problem.
If you can do this repair, more power to you. I'd advise you be extraordinarily careful the youtube videos can be misleading as to the level of complexity you're getting into. Otherwise, find a reputable shop that can get you squared away before the damage goes further and damages the traces on your phone.