Stop your Mac from singing the Bluetooth blues

Q. My Mac shows Bluetooth isn’t available, leaving me without a working mouse. How do I get it back?

A. Having your computer randomly lose sight of a built-in bit of hardware isn’t an experience confined to Windows users. In this case, OS X’s settings can get sufficiently scrambled for it to report that a Mac’s Bluetooth wireless is “Not Available,” with a squiggly line through its dimmed menu-bar icon.

Repairing that involved two steps, each of which evoked 20th-century Mac troubleshooting. It helped greatly that I had a spare corded mouse — another reminder of a different era of Apple computing.

The first one, as outlined in a how-to post at OS X Daily, was to delete a preference file that stored this 2009-vintage iMac’s Bluetooth settings and that had mostly likely gotten corrupted.

“Trashing prefs” was a fairly common cure in the “classic” Mac operating system, and it hasn’t gone out of style in OS X. To get at the ones storing a Mac’s Bluetooth settings, you need to switch to the Finder, click on the Go menu, select “Go To Folder…” and type “/Library/Preferences”--with both forward slashes and without any spaces.

In the Preferences window you’ll now see open, type “bluetooth” into the search form and click the “Preferences” button to the right of the “Search” heading in that window. You should now see a single “com.apple.Bluetooth.plist” file, but you may also spot a second copy of that file with a name ending in “lockfile.”

Delete one or both as necessary. You’ll have to enter your account password each time, because this file technically belongs to the system, not you the user. Then reboot.

(In case you were curious about the “.plist” file-name extension, that’s short for “property list.”)

After trashing that .plist file and rebooting this Mac, Bluetooth was once again available. But pairing various devices was still erratic — and some System Preferences panes looked visually scrambled. So I decided to try a different troubleshooting procedure that Apple’s new and remarkably responsive@AppleSupport Twitter account had suggested when I was working through an unrelated issue: booting into “Safe Mode.”

This troubleshooting option starts up a Mac without any third-party code and flushes out a variety of system caches. You invoke it about in the same way you used to boot an old-school Mac free of all system extensions: by holding down the Shift key until you see the Apple logo on the screen.

Restarting this way took about 20 times longer than normal, thanks to all the disk checks that went on, but then pairing Bluetooth devices worked as advertised — including a dusty Apple mouse that I assumed had stopped working. In reality, the computer’s mysterious failure to see that input device should have been my first clue that its Bluetooth settings were going bad.

If that hadn’t worked, I would have tried one last troubleshooting routine: resetting the iMac’s System Management Controller, a special chip that governs a variety of hardware components. An SMC reset got my MacBook Air’s Webcam back in action when OS X reported it not installed, and the OS X Daily Bluetooth how-to post also endorsed that as a final step.

The steps to reset the SMC vary by Mac, but Apple’s support site has a concise walkthrough of them that also lists the different symptoms of bad juju (for lack for a better phrase) that may require this remedy.

Rob Pegoraro is a tech writer based out of Washington, D.C. To submit a tech question, e-mail Rob at rob@robpegoraro.com. Follow him on Twitter at twitter.com/robpegoraro.