Q: My touchpad is working alone

Go step by step and test.

1. Restart

2. Shut down the computer.

    Clean the trackpad with moist not wet microfiber cloth.

    System Preferences > Point & Click

    Try turning off three finger dragging and then turning it on after  testing.

3. Is there any Bluetooth device nearby with failing batteries? If so, replace the batteries.

4. Reset PRAM:   http://support.apple.com/kb/PH14222

5. Reset SMC.     http://support.apple.com/kb/HT3964

    Choose the method for:

    "Resetting SMC on portables with a battery you should not remove on your own".

6. Close all windows and quit all applications.

    Click the spotlight -the magnifying glass icon- in the menu bar. Enter Disk utility in the box.

    Select Disk Utility from the drop down. When the Disk utility window opens up,

    select  Macintosh HD, then First Aid.

    Click Repair Disk Permissions button.

    Ignore the  time remaining estimate.

    Last 1 minute may take longer.

 
  If this does not solve the problem, you may have to take the computer to the Apple store

to have it checked out.

Best.

I tried everything mentioned above. As I do have 2 trackpads at home , I replaced the "ghost" one , and It worked perfectly. But, luckily, it became unresponsive, as It was being touched all time. I remembered that It could be the rubber in the back panel. When it comes off, it is very hard to but it back correctly, because it comes in folded, making more pressure that necessary. Also, there is no space to unfold it. Than I remembered the 80's caracter MacGyver. I took a paper clip, smashed it with a hammer to make it thin and plain. Than I folded It like an "L". That way too can put it in the rubber hole, and unfold it. Now it is working 100%!!