MacBook Pro Trackpad Failure Catch-22 Solution

The battery in a MacBook Pro swells. This damages the trackpad so that the computer thinks you are permanently holding down the left mouse button. Since you are already clicking, you cannot click. The computer behaves as if your left mouse button did not work. An external mouse does not help, since the trackpad is still sending the blocking signal, preventing the mouse click event from being accepted. The solution is to turn on "Ignore trackpad when mouse is present" in the System Preferences. However, the way you turn this on is with a left mouse click, the one thing you cannot do. Catch-22.

The deeper solution is to open Macintosh HD/Applications/Utilities/Terminal. At the $ prompt type in this command exactly as written:

defaults write -g com.apple.mouse.ignoreTrakpadIfMousePresent 1

Notes: That is a single space between items, a single dash before the g, com.apple.mouse.ignoreTrakpadIfMousePresent is all one word with three periods in it, the last item is the number one. (If it was a zero, it would turn the trackpad back on.)

Hit return. Quit the terminal program. Some sources say to log out and back in, but that did not work for us. We had to shut the computer down and restart it. And then, as long as an external mouse is connected, the computer works just fine. The modern word for miracle is "workaround".


Added note: However, despite the setting, on the MacBook Pro we were trying to fix, any touch of the trackpad overrode the setting and the mouse locked up again. Perhaps something thin taped over the trackpad would prevent this? The owner opted for a new laptop. He was due, anyway.