My Hp laptop model G62 is not charging and it is not the cord

My Hp laptop model G62 is not charging and it is not the cord. The computer will charge just fine for a few days and then it stops charging with the light by the plug will blink from white to red. If I pull the plug and put the plug back in the computer shows that it is pluged in, but only for a few seconds. I have changed the cord and the problem is still there.
The problem is the motherboard, the plugin jack, or the battery. Can I trouble shoot these problems so i do not have to replace them one at a time?

I just noticed that when the computer is in sleep mode or shut off it will charge to 100%.