I had the same problem with my '99 Ford F-150 and fixed it. I will not take credit for ths fix as I read it here or another forum. The problem is a thermister which is a small rectangler piece of metal and is mounted in the motor which in turn is mounted in the actuator. It is a little tricky removing the actuator but can be done. Once you get it out pry it open ( you will bust the little tabs that hold it togeather but not to worry as a little epoxi where the tabs were will hold it togeather when finished. Once you get it apart, remove the motor and reshape the bent tabs that hold it togeather and disassemble the motor. Inside the motor you will find the thermister. Pry it out and wrap it in foil to short is out thus eliminating it from the circuit. Put it all back togeather and wolla you now have working door locks. If you want prove it before reassembling it in the truck hook two small clip leads up to the actuator and hook one to your already disconnected battery (hope you thought of doing this before doning anything else) and then touch the other clip lead to the other battery post. If you don't see the actuator try to move reverse the clip leads on the battery or actuator. after wrapping the thermister in foil and reassembling it thy this again. You will be amazed at the results. Any questions you can leave it here or to my direct e-mail (probley smarter) and I will get back to you. Good luck....Bill.
My e-mail address is
ab0ot@juno.com