Mighty Mouse scrolls up, but not down

You probably just need to clean it:
Use a clean lint-free cloth lightly moistened with water. Wipe the ball and the surrounding area, making sure to rotate the ball itself to ensure complete coverage. If the scrolling feels rough or if the scroll ball isn't scrolling up, down, or side-to-side, hold the mouse upside-down and roll the ball vigorously while cleaning it to help dislodge any particles that may have collected on the internal hardware. Finally, give it a good rap on the desk to get the last bits of gunk out.

Let us know if this cures the problem.

A pleasure!

I found that this method or alternatively some 'air brush' ; a compressed can of dust and lint remover air seems to blow all the gunk out of the system.

MGW wrote:
You probably just need to clean it:
Use a clean lint-free cloth lightly moistened with water. Wipe the ball and the surrounding area, making sure to rotate the ball itself to ensure complete coverage. If the scrolling feels rough or if the scroll ball isn't scrolling up, down, or side-to-side, hold the mouse upside-down and roll the ball vigorously while cleaning it to help dislodge any particles that may have collected on the internal hardware. Finally, give it a good rap on the desk to get the last bits of gunk out.

Let us know if this cures the problem.

Miriam-
You almost always recommend this procedure for cleaning the scroll ball, and this is precisely what Apple suggests.
I've had my iMac for 2 months, and for the past 2 weeks the scroll ball has been increasingly erratic: It doesn't always work when I scroll horizontally, or vertically downward; and it's just about useless when it comes to scrolling vertically upwards. I've repeatedly tried the above procedure to clean the scroll ball, but it hasn't worked.
As I searched the discussion forums, I did find an alternative procedure that is attributed to you: The "rub-the-ball-on-a-piece-of-white-paper" method. I tried it. It immediately worked!!! I am absolutely amazed...+your solution is BRILLIANT!+
Besides offering my deepest thanks for such a gem, I would like to know (1) How did you ever discover it? and (2) Why is it that you always seem to offer Apple's suggestion and not your procedure?

Thanks. Sometimes I simply forget to add the "smack it on the desk" bit, but I'll try to remember to do it from now on. I discovered it by trying to fix a friend's MM.

MGW wrote:
Thanks. Sometimes I simply forget to add the "smack it on the desk" bit, but I'll try to remember to do it from now on. I discovered it by trying to fix a friend's MM.

Smack it on the desk? Nah...I didn't have to do that. Simply turning the MM upside down and rubbing the ball around on a small piece of clean inkjet printing paper was enough. (I still can't believe that worked when the lint-free cloth & water approach didn't!)

Miriam,

A big thank you from me as well. 🙂 I was just about to get violent with my mouse and came across your use-your-mouse-upside-down-on-white-paper tip. At first it didn't do anything, so i sprayed a little bit of rubbing alcohol right on the ball and vigorously rotating the mouse upside down for almost a minute.... then, all of a sudden, it worked again! I will make sure to pass that effective technique to all my mac friends.

Cheers.

amazing.. the paper worked perfect for me

Well, I'm simply amazed that no one seems to mention this method. Even Miriam—to whom this method was attributed by another poster—seems to recommend the "Apple method" in her posts.
I must say that the "Apple method" seems quite reasonable. But, as I previously indicated (as have others), it simply wasn't effective for me. The "rub-the-ball-on-a-piece-of-white-paper" method, on the other hand, is counterintuitive (actually, it seems ridiculous). However, it works amazingly well. One can only imagine that it was born out of a user's frustration when the "Apple method" failed and the user threw a tantrum! 😉
Go figure.

if the scrolling feels rough or if the scroll ball isn't scrolling up, down, or side-to-side, hold the mouse upside-down and roll the ball vigorously

From one of my posts above 😉

MGW wrote:

if the scrolling feels rough or if the scroll ball isn't scrolling up, down, or side-to-side, hold the mouse upside-down and roll the ball vigorously

From one of my posts above 😉

But Miriam, you are quoting the "Apple method" (<http://docs.info.apple.com/article.html?artnum=302417>), which is not the "rub-the-ball-on-a-piece-of-white-paper" method.

Hi. The mighty mouse was a mighty flop. I ended up using pure alcohol in a small airbrush spraygun to fully clean the thing without taking it apart. You have to give it a half hour or so after spraying it out for the alcohol to evaporate then it should be like new. If you can't access a spraygun, either airbrush compressor type or handheld pump spray then you have to fiddle with running a pad soaked in alcohol or another "non plastic damaging solvent" rapidly in all directions over the ball while holding the mouse upside down. That also works but nowhere near as effectively.

I've used alcohol & Q-Tips on my mouse (mice) since my first Apple II computer many years ago. It always works. Just be deliberate and thorough.

Justed wanted to say that the same thing happened to me, my mighty mouse too just stopped scrolling down, it would scroll up, but not down. The fix however did get my mouse working properly and I wanted to make clear the procedure for cleaning it. At first, I went and got a piece of paper off my printer, held the mouse upside down and just started like wiping the trackball and that didn't work. But with an open music book sitting on my desk in front of me, I just turned to mighty mouse upside down on the book with the trackball on the page and just started moving it up, down, round and around. That got it going and now I'm happy that it's working again.