since getting the free El capitan upgrade my bluetooth keyboard and mouse will not connect, I am using my old USB keyboard and mouse, but am experiencing issues with them also. The mouse jumps during use as if it loses connection then reconnects, and the same with the keyboard.
Mac mini (Late 2012), OS X El Capitan (10.11), 2.3, I7, 16MB, 1TB
There are quite a few steps, including the additional Apple Support documents linked at the end of that one. Read and follow everything.
Using your wired devices, reset the PRAM. Then reset the SMC.
Barry
This suggests some software conflict with a kext or driver that is not EC compatible.
You may want to run Etrecheck and post the report it produces here so we can take a look.
There are several possible causes for this issue. Please take each of the following steps that you haven't already tried until it's resolved. Some may not apply in your case.
1. Follow the instructions in this support article, and also this one, if applicable. A damaged or defective AC adapter could be the cause, even if it's the right kind.
2. Press down all four corners of the trackpad at once and release. If there's any effect, it's likely to be temporary, and in that case the unit must be serviced or replaced.
3. Disconnect or power off each Bluetooth or USB pointing device, one at a time, testing as you go. You may be able to identify one that's malfunctioning. By a "pointing device," I mean a peripheral that moves the cursor, such as a trackpad, mouse, trackball, or graphics tablet. A plain keyboard is not a pointing device. If you have a desktop model without a built-in trackpad, at least one external pointing device must be active at all times.
4. If your model has an infrared receiver for use with an Apple Remote, disable it.
5. Start up in safe mode and test, preferably without launching any third-party applications. If you don't have the problem in safe mode, but it comes back when you restart as usual, stop here and post your results. Do the same if you can't start in safe mode. If there was no difference in safe mode, go on to the next step.
6. Reset the System Management Controller.
7. If you're using a Bluetooth trackpad or mouse, investigate potential sources of interference, including USB 3 devices.
8. A swollen battery in a portable computer can impinge on the trackpad from below and cause erratic behavior. If you have trouble clicking the trackpad, this is likely the reason. The battery must be replaced without delay.
9. A defective peripheral device or a damaged cable can cause the built-in trackpad of a MacBook to behave erratically. If you're using any wired peripherals, disconnect them one at a time and test.
10. There's also a report of erratic cursor movements caused by an external display that was connected but not turned on.
11. If you use Handoff, disable it in the General pane of System Preferences.
12. If AirPlay mirroring to a TV is on, turn it off.
13. If none of the above applies, or if you have another reason to think that your computer is being remotely controlled, remove it from the network by turning off Wi-Fi (or your Wi-Fi access point), disconnecting from a Bluetooth network link, and unplugging the Ethernet cable or USB modem, whichever is applicable. If the cursor movements stop at once, you should suspect an intrusion.
14. Make a "Genius" appointment at an Apple Store to have the machine and/or external trackpad tested.
I want to thank everyone for their suggestions and assistance. It was very difficult framing my question with the keyboard or mouse connecting and disconnecting. What I've done is restored to Yosemite 10.5, and all my issues of runaway. Just to be clear I upgraded to El Capitan, and could not make a connection with either my wireless mouse or keyboard. I keep an Apple USB keyboard on hand for just such emergencies. And that is what I used to frame my original question, yet even this direct connect keyboard would connect and disconnect at what seemed to be the rate of a flashing cursor. ( at least that's what I reminded me of.) As I said I've restored to 10.5 and all the issues have gone away. When I have more time I'll try upgrading again, hopefully someone with more time on their hands will run across this issue and Apple can get it solved. Until then I'll stick with Yosemite. Once again thank you for all your efforts.
#2 Worked for me - the track pad immediately got back to normal!! I guess I need to find a shop to get it fixed as I don't have AppleCare 😟 Thank you very much! This problem is driving me nuts! It would go crazy, then after a few reboots would come back to normal for an hour or sometimes for a day and it would start happening again..
mouse uncontrollable
