Black Screen and does not take charge

The Macbook was off for 7 weeks while I was on a business trip combined with vacation. It was fully charged when I left it but it didn´t turn on only with battery power when I first tried after that period. I connected the charger and it booted OK showing 0% charge on the battery. I left it charging but the screen soon went black again and the charger connector light went off. After that I can no longer get a light on the charger connector at all (green or amber) and the computer will not turn on. The charger is good as it works just fine on my other Mackbook Air 13". I fully cleaned the Magsafe connectors (both on the charger and on the Macbook) and also opened the back of the Mackbook to disconnect the battery but that didn´t change anything. The charger does not light up with the battery disconnected or after I reconnected it. I should mention that for several months before I left the computer off the charger light would not light up the first time I connected it to the computer. I had to wiggle the connector up and down a few times and it would take a while before I got any light on the charger connector. Could this be a bad I/O board? I´m ready to order one but I´m afraid to spend $100 and find out later it was a bad logic board.