This happens because the lasers used for reading discs age. They get weaker and weaker the longer they are used. Eventually they are too dim to work.
This repair is not for everyone. It takes a Nintendo triwing screwdriver and a jewelers Philips head screwdriver set, small pliers, soldering iron and I use a magnifying lamp (but I'm old). If you are fairly mechanically inclined, careful keeping track of the screws, cables, etc. You can do it. It took me about two hours and I do this kind of stuff all the time. If this is your first it will probably take a lot longer. Otherwise go for buying a replacement drive, they cost 60 bucks and up, but you avoid the tricky parts of the repair, the soldering, and almost all the ribbon cables.
This Wii was one of the original Wii's, we bought it in November 2006 for Christmas, stood in line and everything. He plays it constantly, and leaves it on all the time. We had already sent it back to Nintendo once for this problem when it was under warranty and they repaired it. I recommend if your Wii is fairly new to go this route. Nintendo is one of the better companies out there for repairing stuff for free, even if it is marginally your fault or a little too long. He didn't want to have a new one, because of all the saved games and downloads on this console. We had to fix this one and I'm cheap and adventurous!
Bought this part on Amazon. It comes with no instructions, and very sketchy details on the description as to what it does or how to use it. No worries!
Brand New Laser Lens for Wii Replacement Part
It did come with the Nintendo screwdriver.
The Wii is much more challenging to open than other consoles and even the Gamecube. There are screws hidden everywhere, under stickers, rubber feet etc. Take you time and find them all. Several guides are out on the web like this one:
This will get the covers off.
The DVD drive has four screws the remove it, two that are obvious and two that you access through holes in the drive near where the disc goes in. They are silver and hold the black plastic down. I admit I unnecessarily took the top cover off the DVD drive, where the disk sits. That meant removing extra screws and risking messing up the plastic gear assemblies in the drive. Don't do this, the laser is not there. Only remove the DVD hold down screws, the laser is on the bottom of the drive.
When you lift the drive there are several ribbon cables that you have to remove. Some plug in, others have tiny clamps on the board that you have to slide back or flip up. This is classic Nintendo construction. The ribbons look much more fragile than they are, but still be careful.
To remove the laser from the drive, you have to take the circuit board up by removing some screws, and then a couple more ribbon connectors. Then there is a sheet metal cover that you have to pry off. It has four clips on each side. It was very difficult to get off, the best way is to stick a screwdriver in from the other side.
Finally you can see the laser. You remove the two screws near the edge that appear to do nothing. They allow you to slide the sliver rails that the laser moves on out of the edge of the case. Take the old laser out, transfer the white plastic triangle that engages the gear from the old laser to the new. Slide it on the rails and push the rails back in.
Note! There is a tiny solder blob on the ribbon cable of the laser. This is protection from electrostatic damage. You will see in the old laser that this blob is divided. You need to use a soldering iron to heat this blob and flick it off. Otherwise the laser will not work.
Whew. I tested it after putting back together a few screws and the ribbon cables. There was one glitch. The drive thought there was a disc in it, mostly because i had taken it apart (see above) when I didn't have to. Couldn't put a disc in. However, pressing eject fixed the problem. A few extra clicks and odd noises and everything snapped back into place. Tried it with a regular CD as the sacrificial lamb, and it went in and out just fine. Time to try a real game. Bingo! It reads the disks. Played some games. Awesome!
OK, now put it all back together.
This is great for your ego, I recommend it to everyone. Makes you a hero to kids who will be asking if you are sure you know what you are doing the whole time.