Hello,
If you've tried everything that's been mentioned then allow me to point out that this is a common problem with gen 3 Explorers, Mountaineers, & Navigators. I recently fixed this same problem. In order to correct this problem you will need to take the inside door panel off the driver's side door (there are some really good videos on YouTube) & gently peel back the piece of foam, then locate the main wiring harness between the 2 hinges. Pull back the rubber boot & gently push it into the door. Now search through the wires & if you find a thin black wire(20-22 ga.I think) that is broke then you've found your problem. Usually it will be broke right in the middle of that bundle of wires. When Ford designed the wiring harness they didn't make that black wire long enough to allow for the door to fully open & over time that wire weakens & ultimately breaks. It's an easy fix but getting that boot out of your way is the hardest part. As I stated before there are some really good videos to help walk you through the necessary steps. Best of luck,