1996 Ford Explorer

The over drive light is blinking, I took it to a mechanic and he put the computer diagnosis and it gave him a code to replace the neutral safety switch. I did that and the problem stopped for awhile. The next day I use the car and the over drive light turned on again and now the car while im driving, it idles up and then grabs the gear, it does this every 2 minutes, I took it back to the mechanic and he did the codes again and this time it gave him 11 different codes, he noticed that there was a sensor loose so he put it back and locked it in place. No codes this time. Drove it for awhile and no problem until the next day. The problem came back I took it back to the mechanic and he said that it might be something electrical what should I do