1. Power Supply Issues:
* Blown Fuse: Check the fuse(s) specifically designated for the cooling fan in the fuse box (usually under the hood or inside the car, consult your owner's manual). A blown fuse is the most common and easiest fix.
* Relay Failure: The cooling fan is often controlled by a relay. A faulty relay prevents the fan from receiving power even if the fuse is intact. You can test the relay with a multimeter or swap it with a known good relay of the same amperage and rating (again, consult your manual).
* Wiring Problems: Check the wiring harness leading to the fan for any breaks, chafing, corrosion, or loose connections. Look for damaged insulation or melted wires. A visual inspection may reveal a problem, otherwise, a multimeter can test for continuity.
* Temperature Sensor Issues: The fan is usually activated by a coolant temperature sensor. A faulty sensor might not send the correct signal to the relay to turn the fan on, even when the engine is overheating. This requires testing the sensor's resistance with a multimeter, comparing it to specifications found in a repair manual.
* Low Voltage: A weak battery or alternator can lead to insufficient power to operate the fan. Test the battery voltage and alternator output.
2. Fan Motor Problems:
* Failed Fan Motor: The fan motor itself might have burned out or seized up. This requires testing the motor for continuity and resistance with a multimeter (making sure power is disconnected first). If the motor is bad, it needs replacement.
* Fan Motor Wiring: The internal wiring within the fan motor itself can be damaged. This is less common but still possible.
3. Control Module Problems (Less Likely in a 1990 Model):
* While less common in older cars like the 1990 LeBaron, a faulty engine control module (ECM) or similar component *could* theoretically be the culprit if it's responsible for activating the fan. This is a more advanced troubleshooting step and requires specialized diagnostic tools.
Troubleshooting Steps:
1. Start with the simplest: Check the fuse first.
2. Visual Inspection: Carefully inspect all wiring related to the fan for any damage.
3. Relay Test: Test the relay.
4. Temperature Sensor Check: Test the coolant temperature sensor.
5. Fan Motor Test: Test the fan motor for continuity and functionality (ONLY after disconnecting power).
6. Voltage Checks: Verify proper battery and alternator voltage.
Important Safety Note: Working on a car's electrical system can be dangerous. Always disconnect the negative battery terminal before beginning any work. If you're not comfortable working with electricity or automotive systems, take your car to a qualified mechanic. Overheating can cause serious engine damage.
