I need some more information. What is not working? Can you hear the electrical click? Or do you hear nothing at all? Once I have this info, I can point you to the right direction.
remove stud locks
The rear actuators may be working, but the locks themselves may be corroded and in need of opening the door up and spraying them generously with penetrant.
You can find a good nudge in the related link below. CommandoCarAlarms.com
There could be many reasons why the 1993 Grand Marquis make noises when the doors lock. The wiring could be off, or the motor could be going out.
on my 94 grand marquis the password for the doorlocks was a little white sticker on the inside of the trunk lid, kind of in the middle. I hope nobody removed it already.
1st step check fuses
More than likely the gears are stripping on the door lock actuator and will soon fail to work.
There is no way to do this. There are child-proof locks on the sliding doors.
call a locksmith to have them rekeyed (this means the locks stay the same but the key changes) or buy new ones and try to replace them yourself.
Fuse number 23 in the passenger compartment box is blown. It caused the following devices to stop working: Door lock switches (but not the locks), Interior lights, radio lights, A/C climate control, overhead console quit.
On your 1997 Mercury Mountaineer : Open the rear doors from the outside and on the end of the doors near the latch you will see a small lever that is used to select child locks on or off
Same problem, but didn't replace the dome light.The locks will unlock but not lock.