Possible Causes:
* AC Blower Motor Resistor: This resistor controls the fan speeds. A faulty resistor can cause excessive current draw, blowing the fuse, especially when the AC compressor is engaged (adding more load to the system). This is a very common cause.
* Blower Motor: The blower motor itself could be failing, drawing excessive current. A shorted winding inside the motor is a prime suspect.
* Wiring Harness: A short circuit in the wiring harness connecting the blower motor, resistor, and AC system is a possibility. Wires can chafe against metal, especially in older vehicles. Look for damaged, frayed, or melted wires, especially near the blower motor and resistor.
* AC Control Module: The AC control module might be malfunctioning, sending incorrect signals and causing excessive current.
* Compressor Clutch Relay: While less likely to directly blow the blower fuse, a failing compressor clutch relay could cause voltage spikes that affect other components, including the blower motor circuit.
Troubleshooting Steps:
1. Check the Fuse: Before anything else, ensure you're replacing the fuse with the correct amperage. Using a higher amperage fuse is a fire hazard!
2. Inspect the Blower Motor Resistor: This is the easiest and most likely culprit to check first. Locate the resistor (usually behind the glove box or under the dash) and visually inspect it for any signs of burning, melting, or damage. Often, these are just a small circuit board and replacing it is relatively inexpensive.
3. Test the Blower Motor: With the fuse removed, disconnect the blower motor connector. Use a multimeter to test the resistance of the motor windings. A very low resistance or a short circuit indicates a faulty motor.
4. Inspect Wiring: Carefully inspect all wiring related to the blower motor, resistor, and AC system. Look for any frayed, melted, or damaged wires, paying close attention to areas where wires might rub against metal. Repair or replace any damaged wiring.
5. Check the AC Control Module: This is more involved and may require specialized knowledge or tools. It's best to leave this to a professional unless you have experience with automotive electrical systems.
6. Check the Compressor Clutch Relay (Less Likely): If you've ruled out other possibilities, you can test the relay for proper operation. A simple multimeter test will reveal if it's functioning correctly.
Important Note: Working with automotive electrical systems involves risks of electric shock. If you're not comfortable working with electricity, it's best to take your Jeep to a qualified mechanic for diagnosis and repair. Improper repairs could lead to further damage or even a fire.
