HELP!...Mega 2560 problem...

I have and arduino mega 2560 r3 hooked up to my motorcycle, using it for remote ignition. I left my arduino with the shield on the bike for 3 days constantly on...Powered via usb car charger...when i decided to remove the board to make a few modifications i noticed the L led wasn't lit but the sketch was running fine...now I plugged my board on my laptop(the one i always use to upload sketches) it doesnt dettect my board, on other thing i noticed, the L led did light up but very very dimly and when i press reset i can see it blink but again very very dimly...pls anyone help me..

May 6V have been present where it shouldn't be ? If thats the case you may have burned a component. Start out with the schematic and a multimeter to verify that acceptabe voltage levels are present at critical points.

Ok I will try that...as of the moment the board still executes the sketch, but when i power it up with 12v the smd part on the right of the power jack heats up right away, it seems like theres an internal short or something...