* Defective Motor: The most straightforward reason is a manufacturing defect in the new motor itself. This is less common but entirely possible.
* Wiring Issues:
* Loose Connections: Check all connections at the motor, the relay (if applicable), and the fuse. Loose or corroded connections are a common culprit. Wiggle the connections while testing to see if the motor starts intermittently.
* Broken Wires: Inspect the wiring harness for any breaks, chafing, or damage, especially near sharp edges or moving parts.
* Incorrect Wiring: It's unlikely but possible the motor was wired incorrectly during installation. Double-check the wiring diagram against the motor's connections.
* Bad Relay (if applicable): The cooling fan often uses a relay to switch the high current required. A bad relay will prevent the motor from receiving power. Test the relay using a multimeter or replace it as a precaution. Some Cavaliers might not have a dedicated relay; the control might be integrated elsewhere.
* Fuse Issues: Check the fuse for the cooling fan circuit. It may have blown even with a new motor, indicating a short circuit elsewhere in the system.
* Insufficient Power: If the battery is weak or the alternator isn't charging properly, the fan motor might not receive enough power to start, especially if it's drawing high current (like when the engine is hot). Test the battery voltage and check the alternator's output.
* Grounding Problems: A poor ground connection can prevent the motor from functioning correctly. Clean the ground points related to the fan and its circuitry.
* Temperature Switch Issues: The cooling fan should be controlled by a temperature switch or the car's computer. If the switch is faulty, it might not be sending the signal to activate the fan, even if the motor itself is good. This is particularly important if the fan only stops working when the engine reaches a certain temperature.
* PWM Control (Pulse Width Modulation): Some fan systems use electronic speed control. A fault in this circuitry could prevent the motor from running, even if it's receiving some power. Diagnosing this would likely require more advanced diagnostic tools.
Troubleshooting Steps:
1. Check the fuses and relays.
2. Visually inspect the wiring harness for damage.
3. Test the motor's power supply with a multimeter. Make sure you have 12V at the motor's connections when the fan should be running.
4. Check the ground connections.
5. Inspect the temperature switch (if applicable).
6. If the fan has multiple speeds, test both speeds.
If you're not comfortable working with car electrical systems, it's best to take your Cavalier to a qualified mechanic for diagnosis and repair. Trying to troubleshoot electrical issues without proper knowledge and tools can be dangerous.
