Your 24" iMac freezing?
My 24" iMac was on it's way to becoming a very large paper weight. It all started when I updated my system software from 10.4 (Tiger) to 10.5 (Leopard). It seems 10.5 makes your iMac run at a higher speed then 10.4 which heats up your iMac and eventually will cause it to malfunction more and more over time.
At first it was just occasional horizontal mostly black lines that would show up on screen then it became more annoying with my mac freezing more and more frequently. When I moved to a warmer climate I couldn't use my iMac for more than 30 minutes before it would freeze up on me and I could fry an egg on the back with how hot it would get.
I've been researching why my once amazing 24" iMac has gone from a God of the computer world to an over priced paperweight. After many months of reading and debates of would it be best to go back to 10.4 I finally opted for a fan modification.
Now even though I may not know the names to most of the parts inside my Mac or any PC for that matter, I can usually feel my way around things to figure them out. And with what breakdown77 wrote, it gave me a good outline to try with my 24 iMac. Now apparently the inside of a 24" iMac is a lot different than the 20" iMac, which is why I thought I should write this for those out there with the same 24" iMac that I have.
So just like breakdown77, I got two 80mm led fans from RadioShack. I would have gotten them on-line for less but I wanted to get started right away and I didn't want to wait. I am thinking about adding a third fan which if i do I'll get that one on line and a couple more as back ups just in case the fans stop working at some point and they need to be replaced. I opted not to buy a power cord since I had a bunch just laying around from other things. If you are comfortable enough to try this fan modification then you should have no problem cutting on old power supply you have laying around. I used a 9v power supply from an old cordless phone base.
I already had a Dremel but if you are not comfortable using a Dremel you could use a drill and a jigsaw.
It would also be wise to have a vacuum cleaner handy, a can of air and safety goggles. When you cut into plastic small pieces tend to fly everywhere.
Now here is where the feeling around comes into play. To find the best place to place your fans you need to feel for the hottest spot or spots on the back of your iMac.
Mine were towards the upper right of my iMac when looking at the back.
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One thing you should keep in mind is that you should drill the four corner holding wholes of the fans while placing the fan on the inside of your iMac so later you can mark your cut lines from the holes you have just drilled from the outer back of the your iMac's case. This will allow you to place the fan exactly where you need it to be and you run less risk in cutting pieces of your iMac that are needed to screw back the parts you removed in order to be able to make this modification.
To be safe use a smaller drill bit than the screws that came with your fan. That way if you need to make the fan holding holes bigger, later, you can. I opted to use screws that would hold the fan solely from the outside without needing a bolt. That way if I ever needed to remove the fans for whatever reason I would not have to take apart my iMac. If your screws are too long you can use the Dremel or jigsaw to cut them and make them shorter. Just make sure you are very careful doing this. It is very easy to lose a digit or end up needing stitches, if you are not careful.
Once you make your cut outlines all that is left to do is cut out the holes. using two steady hands and extreme caution.
The piece that was emitting the most heat from my iMac was covered by a plastic case. it was easy enough to slip it off the part it covered and place the black plastic case back up against the hole I had just cut out of the back of my iMac so that I knew exactly where to cut into the black plastic case.
I used electrical tape around the holes I cut to hold down the metal like sheet that is in the inside of my iMac. Not sure what the metal like sheet is but I'm guessing it has something to do with protecting the plastic of the iMac from heat.
Note how the fan holes are different angles. This was done because of the aluminum frame inside the 24" iMac. I didn't want to cut away the screw holders of the aluminum frame. Also keep in mind that unless you want to completely remove the aluminum frame from the plastic frame and everything attached inside your iMac, you will need to make that cut with a Dremel.
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Put everything back together and make sure your iMac will turn back on. If your iMac turns on without any problems, shut it down until you have attached the fans.
Since I had two fans I decided to created what I believe to be better air circulation by having the hottest spot blow out air, while the second fan blows in air. I also added a screen covering to protect from dust by cutting a piece of plastic screen I had laying around. You could buy a cover but a rubber band, a piece of screen and a pair of scissors will do the same thing.
Note the fan on the left blows out air while the fan on the right blows in air.
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As I stated earlier I might add a third fan which will be placed just under the fan on the left to bring the temperature of my iMac down even more but for now I've had my 24" iMac on all day and the back of my iMac is cool to the touch and has not frozen once or given me any of those annoying black lines on my screen.
I hoped this helped anyone with a 24" iMac.
