Recently my car remote has been working intermittently. I finally got frustrated enough with it to fix it.
Step 1: Open the remote
Car remotes are pretty simple devices but there are several components that can need replacing; The case, the buttons, the battery, and the board.
To open the remote just remove the screw with a phillips head screwdriver and then use a standard screwdriver to separate the two sides of the case.
Once the remote was open I could see the problem. Part of the battery holder had come unsoldered.