I fixed it - Mac would not go to sleep when the lid was closed

OK, this is not a question because I fixed my Mac and I am hoping I can save someone $350. My Mac would not go to sleep when I closed the lid. In fact it would get really busy and overheat. Disk access also got really flakey. It worked but I spent a lot of time watching the spinning beachball. I replaced the hard drive but could not get it to format. I had put it in my backpack one time when it did not go to sleep and it got really hot. I thought I had fried the motherboard so I replaced the motherboard. It seemed to work better but it still would not go to sleep and spent a lot of time watching the spinning beachball. I pulled the hard drive and and attached it with an external sata-usb adapter and it worked fine. The only thing left to replace was the cable between the motherboard and the hard drive but if a cable fails, it does not get flakey, it just stops working. Anyway, I ordered a replacement. As I was installing it, I noticed that the same cable connected to the sensor that detects that the lid has closed. Coincidence? Replacing that cable and the sensor did the trick. My suspicion is that the sensor was sending noise down the cable when the lid was closed, telling the system to sleep, wake up, sleep, wakeup, etc etc. which spawned a lot of processes that were having a problem completing and caused the activity. I also think that while the lid was open, the noise was messing up the disk connection. Not killing it but making it really slow. Anyway if I had started with a replacement of the disk drive cable and lid sensor, I would have saved the $350 cost of a replacement motherboard. Enjoy