* Cooling Fan Relay: This is a very common culprit. The relay acts as a switch, activating the fan when the engine temperature reaches a certain point. A faulty relay may not close the circuit to power the fan when the engine overheats.
* Engine Coolant Temperature (ECT) Sensor: This sensor monitors the engine's coolant temperature and sends a signal to the PCM (Powertrain Control Module). If the ECT sensor is faulty, the PCM may not receive the correct information to activate the fan. A bad sensor can send incorrect readings, causing the PCM to believe the engine isn't overheating.
* PCM (Powertrain Control Module): While less likely, the PCM itself could be faulty and not sending the signal to activate the fan, even if the ECT sensor is working correctly. This is usually diagnosed last, after other components are checked.
* Fan Control Module (if equipped): Some vehicles have a dedicated fan control module that manages fan speed and operation. A failure in this module could prevent the fan from working when the engine overheats. (Less common in older Cavaliers, but possible).
* Wiring/Connectors: Check all the wiring and connectors related to the cooling fan, the ECT sensor, and the relay. Corrosion, broken wires, or loose connections can interrupt the electrical signal and prevent the fan from working.
Troubleshooting Steps:
1. Check the obvious: Ensure the cooling fan is getting power directly from the battery while the engine is hot (DO NOT DO THIS WHILE THE ENGINE IS RUNNING). If it works when power is applied directly, the problem is with the electrical control system and not the fan motor. Be very careful not to short the fan leads.
2. Check the Relay: Locate the cooling fan relay (your owner's manual or online forums for your Cavalier year should show its location). You can often swap it with another relay of the same amperage rating (if another relay in your car is similar) as a test. If the fan works, the original relay is likely bad.
3. Check the ECT Sensor: This usually has a single or two-wire connection. A multimeter can be used to check if the sensor's resistance changes with temperature. However, this requires some electrical knowledge and the correct resistance chart for your specific sensor. It's often easier and cheaper to just replace it.
4. Check wiring and connections: Visually inspect all wiring and connectors related to the cooling fan, relay, and ECT sensor for any damage, corrosion, or loose connections. Repair or replace as needed.
If you're not comfortable performing these checks yourself, it's best to take your car to a mechanic. Continuing to drive with a non-functional cooling fan when the engine is overheating can cause significant engine damage.
