its electrical. there is a circuit board under the computer, which can corrode and break continuity. You will need to take the left step off to access the problem. The big black box houses the computer, disconnect and remove the computer. The white plastic circuit board is underneath. you will need to remove it. then carefully seperate the halves to access the corrosion. take pics to reassemble properly when done. You will find the break, likely need to solder in a jumper wire from to bridge the gap created by the corrosion. Take you time and lots of pics, it should go fine.