* Fuel Level Sender Unit: This is the most likely culprit. The sender unit is located in the fuel tank and measures the fuel level. It can fail due to:
* Corrosion: Rust and debris can build up and interfere with the sensor's operation.
* Wiring issues: The wires connecting the sender to the instrument cluster can become corroded, broken, or disconnected.
* Faulty sender: The sender itself can simply wear out over time.
* Instrument Cluster (Gauge Cluster): The gauge itself within the instrument panel could be faulty. This is less common than a sender issue but possible.
* Wiring harness: Problems in the wiring harness between the fuel level sender and the instrument cluster can lead to inaccurate or no readings. This includes connectors that may be loose or corroded.
* Grounding Issues: A poor ground connection somewhere in the circuit can prevent the gauge from receiving the correct signal.
* Fuel Pump Module (less likely): While less common, issues within the fuel pump module *could* affect the sender unit's ability to function correctly.
Troubleshooting Steps:
1. Check the Fuel Gauge: Does the gauge move *at all*? If it doesn't move at all, the problem is likely with the sender or wiring. If it fluctuates wildly or intermittently, the problem is likely with the sender or wiring.
2. Check the Wiring: Inspect the wiring harness leading from the fuel tank to the instrument cluster for any damage, corrosion, or loose connections. Pay close attention to connectors.
3. Check the Fuel Level Sender Unit: This usually requires dropping the fuel tank (a significant job). You'll need a fuel pump removal tool and safety precautions for working with fuel. This is best left to a qualified mechanic unless you have experience with auto repair. A visual inspection for corrosion might be possible without removal.
4. Test the Fuel Level Sender Unit (if accessible): You can test the resistance of the sender unit using a multimeter, but this also requires some technical knowledge and accessing the sender unit. This is typically done when the unit is removed from the tank.
5. Instrument Cluster Check (last resort): If all other checks are okay, the gauge itself within the cluster may need repair or replacement, which is typically a more expensive fix.
Recommendation: Unless you're experienced with car repairs, it's best to take your 1998 Ford Windstar to a qualified mechanic to diagnose and repair the faulty gas gauge. Replacing the fuel level sender unit is often the solution but requires specialized knowledge and tools.
