All of a sudden the power windows do not work on driver or passenger side? Checked fuse panel on driver is side of dash
board. Also checked relay box panel under hood?? What is left? Could it be a loose wire???? Help with this would be great.

Have you tried to find out what is behind the panels of the inside side of the doors? l understand the system could have some modules.Try it removing those panels and you will also find the motors for the window glass. Check them by connecting directly to the battery. If they work then, check some switches.If after checking all and finding all alright,the job is for experts.

more then likely it is the switch. but it should be tested before you go and replace it.

Open the boot between the body and the door and look for a broken wire.

l also have the same problem with my 1998 Mountaineer.
2 days ago the window control was intermitt. It would begin working after shutting the door hard. l also have checked the fuses, the relays, the sw. but all with no help. l even trided a sw. from the salvage again no help.
If you do find something please post!