I am having the exact same problem right now on my 91 Bronco. My passenger side totally stopped working a couple weeks ago. And the driver side goes half way sometimes and makes a funny noise as well. I was gonna go price some actuators sometime soon. Let me know if you get any prices or a ballpark figure.
Those electric door locks have small electric motors in them and they do get intermittent. The problem is that dampness will get into them. I have a 91 and I have had to fix and replace mine twice. I don't know about 99's but on mine there is a 1/4 heavy duty pop rivet that holds the bracket to the door and I had to drill it out. You could pop the motor out of the bracket without doing this but there is not enough room to get any leverage with your hand. once you get it out you can try to lubricate the spiral driven actuator with some lubriplate. If the rubber cover for the motor is ruptured you might try to make a new cover out of plastic sheet and attach it with a plastic staystrap. If the motor is still intermittent then it will have to be replaced. Ford charges dearly for them. I have removed them from other Ford products in savage yards. You can take the spiral actuator off of yours and swap it with the assemblies from other Ford vehicles. Good Luck.
Art
Christ> I have a 99 F-150. Last spring, my dad and I tinted the windows ourselves.
I've got a '99 F-150 myself. Chris, chances are you got moisture on the contacts or in the motor. This occurs when your wetting solution is sprayed from the inside. (The rubber gasket on the outside avoids this situation from the weather. If it's salvageable - you can remove the door panel completely. (Not difficult to do) The door locks and electric windows have cluster sockets that easily remove as well as the courtesy light at the heel of the armrest. Take a hair dryer (or a sunny warm and breezy day) and allow it to dry thoroughly. Don't use the hair dryer with a partially opened panel - the moisture will remain in the door cavity. Let it completely dry and give it a shot. If it will work at all - it should do it now. If not, begin the replacement process.
Jim
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