On my 2001 Ford F-250 the power locks aren't working properly. When you hit the button the locks try to go down or up but they won't go all the way. You can hear the acuators working in both doors but they won't go all the way down or up all the way. (won't work with the keyless remote either). I changed both acuators in each door and didn't fix the problem. Does anybody know what it could be?

 

They are worn out (weak). There is a rebuild kit available from the dealership.