1. Identify the Problem:
* Does the cruise control engage at all? This points to a more serious electrical or vacuum issue.
* Does it engage but disengage unexpectedly? This could be a speed sensor, vacuum leak, or switch problem.
* Does the set speed not hold? Again, points to a speed sensor, vacuum leak, or a problem with the servo motor.
* Do the cruise control lights not illuminate? This suggests a fuse or wiring problem.
2. Check the Obvious:
* Fuses: Check the fuse box (usually under the hood and/or inside the van) for blown fuses related to the cruise control system. Your owner's manual will show the fuse layout and ratings.
* Brake Pedal Switch: Make sure the brake pedal switch is working correctly. If it's faulty, depressing the brake will always disengage the cruise control. You can test this with a multimeter or by visually inspecting the switch for damage.
* Clutch Pedal Switch (if applicable): Manual transmission Windstars have a clutch pedal switch that functions similarly to the brake pedal switch.
* Vacuum Lines: Cruise control in this era often uses vacuum. Inspect all vacuum lines connected to the cruise control system for cracks, leaks, or disconnections. A hissing sound near the engine bay might indicate a leak.
* Steering Wheel Switch: Carefully inspect the steering wheel controls for any damage or loose connections. Try cleaning the switches with contact cleaner.
3. More Advanced Troubleshooting:
* Speed Sensor: A faulty vehicle speed sensor (VSS) will prevent the cruise control from functioning. This sensor is usually located on the transmission. You'll likely need a scan tool to check the VSS signal.
* Vacuum Pump/Reservoir: If you've checked for leaks and still suspect a vacuum problem, inspect the vacuum pump and reservoir. Low vacuum pressure will prevent the cruise control from operating correctly.
* Cruise Control Servo: The servo is the component that actually controls the throttle. A faulty servo will need replacement. Testing this requires specialized tools or knowledge.
* Wiring Harness: Inspect the wiring harness connecting the cruise control components for any damage, chafing, or broken wires. This can be a tedious process.
* Throttle Position Sensor (TPS): A faulty TPS can interfere with cruise control function. A scan tool is needed to check its readings.
4. Repair/Replacement:
* Repairing vacuum leaks: involves replacing damaged vacuum lines or sealing leaks.
* Replacing faulty switches or sensors: requires purchasing the correct replacement parts and installing them according to the vehicle's repair manual.
* Replacing the servo or other internal components: often requires professional assistance due to complexity.
Important Considerations:
* Repair Manual: A factory service manual (FSM) for a 1998 Ford Windstar is highly recommended. This will provide detailed diagrams, component locations, and troubleshooting procedures. You can often find these online (e.g., eBay).
* Professional Help: If you are not comfortable working on your vehicle's electrical or vacuum systems, it's best to seek professional help from a qualified mechanic. Improper repairs could lead to further damage or safety hazards.
* Scan Tool: A scan tool (OBD-II code reader) can help diagnose problems by reading trouble codes from the vehicle's computer.
This is a comprehensive guide, but each situation is unique. Carefully follow the steps, and if you're unsure about any step, consult a professional. Safety first!
