I also have nonfunctioning electric door locks.
I bought a new one, and didn't get up the ambition to takle it yet.
The actuator is a motor that pushes and pulls a rod. It is mounted to the door near the bottom vertically. It snaps into a plastic retainer that is riveted to the door. If one opens the door, and looks below the door locking mechanism, one will see a dime sized washer looking thing that has a rivet in the center of it. That holds the plastic clip/holder that holds the actuator in place. On my bronco that plastic holder is broken on both doors. I guess I am going to have to drill the center of the rivet out, and use a bolt or something to hold the new plastic holder in place.
I pulled the actuator out and put power to it a few differnet ways to test it, and nothing happend so I guess it is bad.
I searched for a helpful thread here and didn't find one that was particularly helpful.
AS you work your way through the problem, see if you can take some pictures, and kinda write a tutorial of how you tested it, and ultimately fixed it.
I found that trying to look at the inside of the door was challenging, and ended up taking my digital camera out, sticking it inside the door and snapped a few pictures. I am not clear on how or where the actuator is suppossed to hook up to the locking mechanisim, cause the parts are lying on the bottom of my door.
If I get to it first, I can help you out... if you get there first, you'll be helping me.
good luck to both of us.
joe