It depends on the vehicle.
with pics! http://www.eurekaboy.com/f250/doorremove.htm
install an alarm system and door lock actuators..
Not any relays, there are actuators inside the doors that move the lock mechanism. Also your switch in the door, the fuse, and the wires.
If you are having problems with interior door locks on a Ford around that year it is most likely the door lock actuators. There is one on each door. They are very prone to fail on those vehicles. On several occasions I have had to replace every single door actuator on Fords of that age. The actuator is behind the door panel, and fairly easy to access once the panel is off. I don't believe door lock actuators are very expensive for that vehicle, but you may want to have a repair shop verify that is the problem.
If it is a coupe there are two. If it is a sedan there are four.
how do you replace rear door lock assembly on 92 pONTIAC tRANSPORT
To fix the power door locks on a 2002 Ford Windstar, start by checking the fuse related to the power locks in the fuse box; replace it if it's blown. If the fuse is fine, inspect the wiring and connectors in the door for any signs of damage or corrosion. You may also need to test the door lock actuators with a multimeter to determine if they're functioning properly. If necessary, replace any faulty components, such as the actuators or switches.
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The door lock actuators are pneumatically actuated by a pump that is located under the rear deck. Any door that has a key, trunk included, also has a switch built into the actuator that controls the pump. - When you turn one of the lock cylinders the key turns the actuator for that door closing a contact. The contact turns on the pump and either pressurizes the tubes going to the actuators, or applies a vacuum to move the actuators to the desired position. Hope this helps.
To replace a sliding door lock, first remove the old lock by unscrewing it from the door. Then, install the new lock by following the manufacturer's instructions and securing it in place with screws. Test the new lock to ensure it functions properly.
To replace a storm door lock, first remove the old lock by unscrewing it from the door. Then, install the new lock by following the manufacturer's instructions and securing it in place with screws. Test the new lock to ensure it functions properly.
To replace a sliding glass door lock, you will need to remove the old lock by unscrewing it from the door. Then, you can install the new lock by following the manufacturer's instructions and securing it in place with screws. Make sure the new lock is compatible with your door before installing it.