97 Grand Cherokee Laredo power locks problem

[xxoutlaw]

I have had my 97 ZJ for about 2 years now. The front passenger door lock has pretty much only worked manually during that time. It would only occasionally work with the power lock or key fob (usually unlock but not lock). Now the locks on all the doors are sporadically failing on me. I am not sure where to start looking. Any suggestions? I haven't found any broken wires. Could I possibly fix it if I replace the door lock switches? Thanks for any help you might be able to provide.