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Many users have reported Mac Bluetooth issues that cause connected devices to behave erratically. These problems resulted in my Wireless Keyboard, Magic Trackpad and Mouse not working correct fly (i.e., erratic cursor movement) and disconnecting frequently.
In this post, I describe the steps I took to troubleshoot the Bluetooth issues I have had on my Retina 5K iMac running macOS.
Keyboard And Trackpad
The connectivity issues started a few years ago with my Bluetooth accessories becoming intermittently unresponsive, resulting in erratic cursor movements and clicks that I didn’t cause.
After some initial troubleshooting, I disconnected the Trackpad and paired my old Magic Mouse. After a few days without issues, the Magic Mouse started acting up as well, followed by my Wireless Keyboard sometimes not registering keystrokes.
After every “reconnect” or a reboot, the devices would work for a while. However, after a few days, the connectivity issues would resurface.
I had OS X 10.11 Public Beta installed and figured the problem was either caused by a corrupt OS X installation or interference. I also learned that the OS X kernel could only handle a limited number of concurrently connected Bluetooth devices without running into congestion and interference issues.
That magic number appears to be 5 or 6; some even say it is as low as 4. But I only had three devices connected at the same time. Because it was unlikely that all three devices had defects, the cause had to be the iMac’s hard- or software.
Unsuccessful Troubleshooting Steps
I did some research and found dozens of potential causes and fixes for Bluetooth issues on OS X. Not knowing the exact cause I tried most of them without success.
Ultimately I ended up having the antennas and AirPort card of the iMac replaced. Since hardware issues are not very common, I ran through the following steps first, before taking my iMac to the Apple Store:
I powered down the iMac and before booting it up into Safe Mode, I replaced the batteries of all three affected devices.
In addition to using fresh batteries, I took a piece of aluminum foil, rolled it into a tiny ball and put it into the battery compartment before inserting the batteries. Some users reported their issues were caused by batteries not having proper contact on either side of the battery compartment.