Updated December 18th, 2015.
When things don’t work properly on a Mac we usually think it’s either a software bug, a problem with preferences, a software interaction the user isn’t aware of, or maybe user error. Thanks to Apple’s excellent quality control we rarely suspect a hardware issue, but sometimes the hardware is the problem. Here are two real-life examples I ran into in the last couple of weeks.
Mysterious Mac Problem #1
The user called me and said that he couldn’t click on anything. The mouse pointer moved but clicking had no effect. This was on an iMac that I’d set up only a week before (and of course I had used the mouse to set it up, so I knew that the mouse had worked). Restarting didn’t help, and neither did signing in as another user. Changing batteries on the mouse (which was wireless) also didn’t help. Very mysterious.
Having given all of the easy suggestions over the phone, and having none of them work, I went to the site to see it in person. Indeed, I could not click on anything either. I noticed that the Mac’s original Magic Mouse was not being used, as a more sophisticated Logitech mouse was favored by the iMac’s user. I disconnected everything but power, then connected my own little portable USB mouse– and that didn’t work either. Now I was really stumped.
Then I had an idea. “Where is the original Apple mouse that came with this machine?” I asked. The user pointed to a small bin, full of cables, CDs, and assorted Mac-related stuff. I dug in and found the mouse… and what do you know, its power switch was in the “On” position. The weight of the other stuff in the bin had been pressing down on the mouse. With the bin within Bluetooth range of the iMac the original mouse’s click was being sent continually, and since a click was already being registered there was no way the machine would respond to a second click (from either the fancy Logitech mouse or from my simple USB model). I solved the problem by turning off the original Apple mouse. Everything worked fine after that. And no, I do not know why I had the idea of looking for the original mouse. It was just one of those things.
Mysterious Mac Problem #2
The user (my own Dad!) sent me an an email every couple of weeks telling me that his iMac wouldn’t sleep. Or, rather, that the iMac would sleep, and then wake up on its own. This went on for months and I could not find an answer, though I suspected that some USB device was malfunctioning and sending signals to the Mac and woke it up. I more or less gave up on solving this one since I was doing the work remotely and couldn’t do any process-of-elimination-by-disconnecting-various-USB-things testing. Yes, I could have had Dad do it, but it’s hard to do with older eyes and I didn’t want to chance not getting things put back together properly. So we let this problem ride.
Then a new problem arose: whenever Dad typed the letter “L” (upper or lower case) it came out with a series of plus signs after it. So, the word “Lollipop” would look like this: “L+++ol+++l++ipop.” This went on for a few days before I knew about it because Dad was careful to go back and delete the plus signs before sending me emails. (Dad also got good at avoiding words with the letter “L” in them.)
For this problem I suspected the keyboard. We were able to demonstrate that the keyboard itself was the problem by using the Keyboard Viewer app (see System Preferences/Language & Text/Input Sources and check the box next to “Keyboard and Character Viewer.” Also check the box that says “Show Input menu in menu bar.”). Every time Dad used the keyboard to type an “L” I could see the “+” also being pressed. But when we CLICKED on the “L” in the Keyboard Viewer app, the only key that showed it was being pressed was “L.”
So now we were almost sure it was the keyboard. Dad got a new one (the Apple Keyboard with Numeric Keypad) and it solved the unwanted “+” problem. Turns out, it also solved the iMac wouldn’t sleep problem. I believe that keys were shorting out on Dad’s original keyboard, either typing the wrong keys when the right keys were pressed, or simply typing by themselves.
(I don’t see a lot of keyboards go bad like Dad’s did. However, Dad smokes cigarettes at his computer, and the smoke gets into things like keyboards and gums things up. I hear it also does bad things to your lungs, and they can’t be replaced with a quick trip to the Apple Store.)