Beatrice Lang
If the electric fan in your Jeep XJ isn't working, there are a few things you can try to troubleshoot the problem. First, check the coolant temperature sensor and relay. If the coolant temperature is above a certain threshold (either 190°F or 103°C, depending on your model), the radiator coolant temperature switch should close, allowing current to flow through the fan relay and activating the fan. If the fan still doesn't work, try checking the fuses and supplying power directly to the relay. If the fan kicks on, you may need to replace the coolant temperature switch. You can also try disconnecting the coolant temperature switch, but this will cause the 'check engine' light to come on.
| Characteristics | Values |
|---|---|
| Fan not turning on | Check for blown fuses |
| Check for faulty relay | |
| Check for faulty wiring | |
| Check for faulty temperature sensor | |
| Check for faulty PCM | |
| Check for faulty fan diode assembly | |
| Check for faulty radiator temperature switch | |
| Fan runs continually | Disconnect battery |
| Fan runs when coolant temperature is above 103°C (217°F) | Relay is energised |
| Fan runs when coolant temperature is below 103°C (217°F) | Relay is de-energised |
| Fan runs when coolant temperature is above 190°F (88°C) | Radiator coolant temperature switch closes, allowing current to flow through the fan relay |
| Fan runs when coolant temperature is below 190°F (88°C) | Radiator coolant temperature switch opens, preventing the relay from being grounded |
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What You'll Learn
Check the relay and fuse box
If your Jeep XJ's electric fan is not working, you should check the relay and fuse box. The relay is the power source for the fan, so if you remove the power source and the fan still runs, it is getting power from somewhere else. The fuse box would be a logical place to start.
You can perform a simple voltage test on the light blue wire to determine if the power is coming from the fuse box or elsewhere. If the fuse box is the source, you will need to inspect the fuses. Check your Jeep's manual to identify the correct fuse for the electric fan. If the fuse is missing, as in one example, or blown, you will need to replace it.
In another instance, a Jeep owner found that their cooling fan fuse had melted. If the fuse has physically melted, then the connections at the fuse are bad and will need to be repaired. If the fuse has blown, then it's possible the fan is going bad and drawing excessive current. In this case, you will need to replace the fuse with one that can handle the required amps.
In some cases, the problem may not be the fuse but the relay. You can test the relay by using a jumper wire with an inline 25-amp fuse to supply battery voltage to terminal 4 of the relay connector. If the fan operates, the motor is good. If the fan motor does not operate, check continuity between terminal 4 of the relay connector and body ground connections on the fender panel back from the relay connector. If continuity exists, replace the fan motor. If continuity is not found, repair and retest.
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Test the fan circuit
To test the fan circuit of a Jeep XJ, you can use a multimeter or a jumper wire with an in-line 25-amp fuse. Here is a step-by-step guide:
- Check the fuse box: Start by checking the fuse box to ensure that the fan is not receiving power from another source. Look for any blown fuses and replace them if necessary.
- Test the voltage: Use a multimeter to test the voltage on the light blue wire in the fuse box. This will help determine if the power is coming from the fuse box or elsewhere.
- Disconnect the fan connector: With the engine off, disconnect the electric fan connector. You may need to remove the fan retaining screws and lift the fan out to access the connector.
- Use a jumper wire: Connect the jumper wire with an in-line 25-amp fuse across terminals 1 and 4 of the relay connector.
- Observe fan operation: If the fan motor operates, leave the jumper wire in place and proceed to the next step. If the fan does not operate, repair the fan relay fuse link.
- Check battery voltage: Check for battery voltage at terminal 2 of the fan relay connector. If battery voltage is not present, replace the fan diode assembly.
- Connect the jumper wire to the radiator temperature switch: With the engine running, connect the jumper wire across the radiator temperature switch harness connector.
- Observe fan operation again: If the fan operates, proceed to the next step. If it does not operate, replace the radiator temperature switch once the engine has cooled down.
- Re-check battery voltage: With the engine running, air conditioning on, and the fan relay removed, check for battery voltage at terminal 2 of the fan relay connector again. If battery voltage is not present, replace the fan diode assembly.
Additionally, you can perform a quick test to determine if the relay and fan are working by using a jumper wire to jump across terminals 1 and 4 of the relay connector. If the fan motor operates, the relay and fan are functional.
It is important to consult a repair manual or seek professional assistance if you are unsure about any of these steps or if the issue persists.
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Check the coolant temperature
Jeep Cherokees have two coolant temperature sensors. One is at the front of the engine in the thermostat housing, and the other is at the back driver's topside of the engine cylinder head, just to the right of the valve cover. The one at the back sends temperature readings to the gauge in the Jeep's dashboard.
To check the coolant temperature, you can use a coolant temperature sensor. The coolant temperature sensor monitors the temperature of the water in the engine. The PCM uses this temperature reading to adjust the fuel injection and timing. In some cases, the PCM uses the reading from the sensor to turn on the electric cooling fan.
If your Jeep Cherokee XJ is not equipped with air conditioning, the relay is energised when the coolant temperature is above 103°C (217°F). It will then de-energise when the coolant temperature drops to 98°C (208°F).
If your Jeep Cherokee XJ is equipped with air conditioning, a two-gang A/C high-pressure switch is also used to control the cooling fan operation. When equipped with this high-pressure switch, the cooling fan will not operate every time the A/C clutch is engaged. In this case, the relay is energised when the coolant temperature is more than 190°F (88°C). The radiator coolant temperature switch closes, allowing current from the ignition switch to flow through the fan relay to ground, activating the relay. When the relay is activated, battery voltage is supplied to the fan, causing it to operate.
Anything in the 200–230°F range for the 3.6L engine is probably nothing to worry about. Temperatures in the 240°F range are not unheard of.
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Check the radiator
The radiator is a crucial component of your Jeep's cooling system, and regular checks are essential to ensure optimal performance and prevent overheating. Here are some detailed instructions on how to check the radiator of your Jeep XJ:
- Start by locating the radiator and identifying the coolant reservoir attached to it.
- Make sure the engine is cool before opening the reservoir cap to avoid scalding.
- Look for the "Full" and "Low" level markings on the reservoir. If the coolant level is below the "Low" mark, you'll need to add more coolant.
- When adding coolant, always use a 50/50 mix of distilled water and coolant to maintain the correct concentration.
Inspect for Leaks:
- Regularly inspect the radiator for any signs of leaks. Look for wet spots, coolant stains, or dripping fluid around the radiator and its hoses.
- Leaks can lead to coolant loss and overheating, so if you notice any leaks, have them repaired as soon as possible.
- The radiator cap plays a vital role in maintaining the cooling system's pressure.
- Inspect the cap for any damage, such as cracks or a worn-out gasket.
- Ensure the cap fits securely and forms a tight seal when closed.
Test the Radiator Fan:
- The radiator fan is responsible for drawing air through the radiator to cool the coolant.
- With the engine off, inspect the fan for any visible damage or debris that may hinder its operation.
- You can test the fan by following these steps:
- Start the engine and let it idle.
- Turn on the air conditioning (A/C) to place an additional load on the system.
- Carefully disconnect the wire plug from the Coolant Temperature Sensor on the thermostat housing.
- If the fan starts running within 10 to 20 seconds, it indicates that the fan and its electrical components are functioning correctly.
- Reconnect the wire plug, and the "Check Engine" light should turn off after a while.
Maintain and Upgrade the Radiator:
- Regular maintenance is key to radiator health. Flush and refill the cooling system as per the manufacturer's recommendations.
- Consider upgrading to a high-performance aluminium radiator, such as the Mishimoto radiator, which offers a 90% increase in coolant capacity for Jeep Cherokee XJ models from 1989 to 2001.
- Keep in mind that extreme driving conditions may require a more robust cooling system.
Remember, a well-maintained radiator is key to preventing overheating and ensuring the longevity of your Jeep XJ's engine.
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Test the fan motor
To test the fan motor of a Jeep XJ electric fan, you can use a jumper wire with an inline 25-amp fuse. First, jump across terminals 1 and 4 of the relay connector. If the fan motor operates, leave the jumper wire in place and proceed to the next step. If the fan motor does not operate, repair the fan relay fuse link. Refer to the wiring diagrams for the circuit diagram.
Next, check for battery voltage at terminal 2 of the fan relay connector. If battery voltage is not present, replace the fan diode assembly. With the engine running, the A/C on, and the fan relay removed, check for battery voltage at terminal 2 of the fan relay connector again. If battery voltage is not present, replace the fan diode assembly.
Now, with a fan relay removed, turn the ignition switch to the "RUN" position. Check for continuity between terminal 5 of the relay connector and body ground connections on the fender panel back from the relay connector. If continuity exists, proceed to the next step. If continuity is not found, repair the open connection and retest.
Finally, using a jumper wire with an inline 25-amp fuse, supply battery voltage to terminal 4 of the relay connector. If the fan operates, the motor is good. If the fan motor does not operate, check for continuity between terminal 4 of the relay connector and body ground connections on the fender panel back from the relay connector. If continuity exists, replace the fan motor. If continuity is not found, repair the open connection and retest.
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Frequently asked questions
Here are some ways to test the electric fan in your Jeep XJ:
- Check the fuse box to see if the fan is drawing power from there.
- Check for battery voltage at terminal 2 of the fan relay connector.
- Disconnect the fan connector and use a jumper wire to test the relay and fan circuit.
- Check the coolant temperature sensor by starting the engine and removing the wire plug from the sensor on the thermostat housing. The fan should turn on after 10-20 seconds.
- Refer to your Jeep's wiring diagram to identify any issues in the circuit.
There could be a few reasons why your electric fan is not working:
- A blown fuse or a short circuit.
- A faulty fan diode assembly.
- A faulty radiator temperature switch.
- A faulty coolant temperature switch.
- A faulty relay or power source.
To replace the electric fan in your Jeep XJ, follow these steps:
- Remove the fan retaining screws from the radiator upper crossmember.
- Disconnect the electric fan connector.
- Lift the fan straight up and out of the vehicle.
- Align the lower retaining tabs of the fan shroud with the slots in the bracket at the bottom of the radiator.
- Push the new fan down into position and tighten the mounting screws.
- Connect the auxiliary cooling fan electrical connector.
There are a few signs that your electric fan may need to be replaced:
- The fan is not turning on at all, even when the engine is hot.
- The fan is making unusual noises or vibrating excessively.
- The fan is not spinning as fast as it used to, indicating a possible issue with the motor.
- The fan blades are damaged or bent, causing imbalance and improper airflow.
Here are some precautions to take while testing or replacing the electric fan in your Jeep XJ:
- Ensure the engine is cool before performing any work on the cooling system.
- Disconnect the battery before working on any electrical components to avoid short circuits.
- Wear gloves and eye protection to prevent injuries while handling sharp metal parts and electrical components.
- Refer to the Jeep's service manual or seek professional assistance if you are unsure about any steps.
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