Door locks

I have a 2001 F-250 and the auto door locks quit working. The remote and the button inside both give the same result nothing. When you push the lock button it makes a noise like its going to lock and the stem on the door moves a little but dosen't lock.
And each time you push the button it gets weaker and weaker untill it stops doing any thing for at least a min. Same result on all the doors. Any advise would be great.