Here's how you can test the relay:
1. Locate the Cooling Fan Relay:
* Consult your Windstar's repair manual: This is the best way to pinpoint the relay's location. It's often in the underhood fuse box, but the exact location varies slightly by model and year.
* Look for a fuse box diagram: The diagram should label the relay. It might be labeled "Cooling Fan," "Radiator Fan," or something similar. Many times it's a larger relay than the others.
2. Visual Inspection:
* Before testing, visually inspect the relay. Look for any obvious signs of damage, such as burn marks, melted plastic, or corrosion. If you see any damage, replace the relay.
3. Testing with a Multimeter (Most Reliable):
You'll need a multimeter set to the appropriate resistance and voltage settings.
* Remove the Relay: Carefully remove the relay from its socket.
* Resistance Test (Coil): Set your multimeter to the ohms (Ω) setting. Test the resistance between terminals 30 and 87 (or the equivalent on your relay; some relays use different terminal numbers; your repair manual is essential here). You should get a reading of a few ohms (usually between 20 and 50 ohms, but this can vary). A very low reading (close to 0) or an infinite reading (OL) indicates a faulty relay.
* Continuity Test (Contacts): With the relay removed, place your multimeter leads on terminals 85 and 86. You should have continuity (a low resistance reading, near 0 ohms). This checks the coil circuit. This isn't as crucial as the resistance test of 30-87, but it's a good secondary test.
* Voltage Test (in-circuit, after repair/replacement): After you've tested the relay itself, put it back in. You'll need to use your multimeter in the voltage setting (DC Volts). With the engine running and the cooling fans *supposed* to be operating (hot engine), test the voltage across the terminals connected to the relay controlling the fan. You *should* see battery voltage (around 12V). If you don't see battery voltage there, the issue might be the fan's control circuit, rather than the relay itself.
4. Testing without a Multimeter (Less Reliable, but Possible):
This method isn't as precise but can help determine if the relay is completely dead:
* Relay Swapping: This is often the easiest method. Find a relay of the same amperage rating (check the relay's markings for amperage) in the same fuse box that *isn't* critical (e.g., don't swap out your headlights' relay!). Carefully swap the suspected cooling fan relay with the spare relay. If the cooling fans now work, the original relay was faulty. Make sure you put the relays back in their correct positions!
Important Considerations:
* Cooling Fan Motor: A faulty relay is a common cause of cooling fan problems, but the fan motor itself could also be defective. If you've tested the relay and it's good, you'll need to test the fan motor directly to ensure it's receiving power and functioning correctly.
* Wiring: Damaged or corroded wiring in the cooling fan circuit can also cause issues. You may need to visually inspect wiring and connectors for any damage.
* PCM (Powertrain Control Module): In some cases, a problem with the PCM's control signals to the relay could be at fault. This is more complex and usually requires professional diagnosis.
If you're uncomfortable performing these tests, it's best to take your Windstar to a qualified mechanic for diagnosis and repair. Incorrect testing could lead to further damage. Remember to reconnect the negative battery terminal after you've finished.
