* Radiator Fan Motor: This is the most obvious possibility. The motor itself could have burned out, the brushes are worn, or there's an internal short.
* Radiator Fan Relay: The relay is an electrical switch that activates the fan motor. A faulty relay will prevent the fan from turning on, even if the motor is good. Jeep Grand Cherokees of that era often have multiple relays, one for high speed and one for low speed.
* Radiator Fan Switch (Temperature Sensor): This sensor monitors coolant temperature and signals the relay to activate the fan when it reaches a certain threshold. A malfunctioning sensor will prevent the fan from engaging. There are often two sensors: one for the gauge and one for the fan.
* Wiring/Connectors: Check the wiring harness and connectors leading to the fan motor, relay, and temperature sensor for damage, corrosion, or loose connections. A broken wire is a common cause.
* Coolant Level: While you're troubleshooting the fan, make sure your coolant level is correct. Low coolant will cause overheating regardless of whether the fan works or not. Check for leaks as well.
* Thermostat: A stuck closed thermostat will prevent coolant from circulating properly, leading to overheating. Even if the fan works, a faulty thermostat will be less effective than it should.
* Water Pump: A failing water pump won't circulate coolant efficiently, contributing to overheating.
Troubleshooting Steps:
1. Check Coolant Level: The first and easiest thing to do. Top it off if needed, but look for leaks if it's low.
2. Check the Fan Relay: Locate the relay(s) (usually in a fuse box under the hood). You can often swap it with a known good relay of the same amperage to test.
3. Test the Fan Motor Directly: This requires some electrical know-how and safety precautions. You can bypass the relay and sensor by directly applying 12V power to the fan motor (using a suitable wire and fuses). If the fan spins, the motor is likely fine and the issue is elsewhere.
4. Check the Fan Switch (Temperature Sensor): This often requires a multimeter to test its resistance at various temperatures. A mechanic's help may be needed for this step.
5. Inspect Wiring and Connectors: Carefully examine the wiring for any visible damage.
6. Check the Thermostat: This might require removing the thermostat housing to inspect the thermostat itself.
7. Check Water Pump: Listen for unusual noises coming from the water pump (whining, squealing). A visual inspection may reveal leaks.
If you're not comfortable doing any of these checks, take your Jeep to a qualified mechanic. Overheating can cause serious engine damage if not addressed promptly.
