Try these steps:
1. Locate the stalk: Find the stalk on the left side of your steering column. It's usually the same stalk that controls the front wipers.
2. Look for a rear wiper switch: This switch might be:
* A separate button: A small button near the top or bottom of the stalk specifically for the rear wiper.
* Part of a multi-position lever: A lever that you pull upward, usually to one position for intermittent and another for continuous wiping. Experiment with different positions of the lever. Often, there's a small upward flick of the lever to activate a single wipe.
3. Experiment with the stalk: Gently move the stalk in different positions—up, down, and possibly pull and push. Listen for the sound of a relay engaging or the wiper motor activating.
If you can't find it or get it working, consult your owner's manual. It should have a diagram or description of the controls. If you don't have the manual, you can often find a PDF version online by searching for "2003 Lincoln Navigator owner's manual."