Possible Causes:
* Blower Motor: The most common culprit. The motor itself might be failing, its brushes worn out, or it could be seized.
* Blower Motor Resistor: This component controls the fan speeds. A faulty resistor can prevent the fan from working at any speed or only at a single, usually high, speed. Often, this manifests as the fan not working at all.
* Blower Motor Relay: This electrical component switches power to the blower motor. A bad relay will prevent the motor from receiving power.
* Wiring and Connectors: Corrosion, broken wires, or loose connections in the wiring harness leading to the blower motor can interrupt the electrical circuit.
* Fuse: While less likely if the AC is working (as that suggests other circuits are fine), a blown fuse is still possible.
* Control Panel/Switch: The switch controlling the fan speed could be faulty. This is less common, but possible.
* Body Control Module (BCM): In some cases, the BCM could be malfunctioning, sending incorrect signals to the blower motor. This is less likely, but a possibility.
Troubleshooting Steps:
1. Check the Fuse: Locate the fuse for the blower motor in your owner's manual or online. Check if it's blown (look for a broken filament). Replace if necessary.
2. Listen Carefully: Turn the ignition on and cycle through the fan speeds. Listen closely near the blower motor (usually located behind the glove compartment). Can you hear any clicking, whirring, or other sounds? A faint whirring could indicate a weak motor, while no sound suggests a complete failure or electrical problem.
3. Check the Blower Motor Resistor: This is often located near the blower motor. Access requires removing the glove compartment or other interior panels. Inspect it visually for any obvious damage (burn marks, melted components). Replacing this is often a relatively inexpensive repair.
4. Inspect Wiring and Connectors: Carefully examine the wiring harness leading to the blower motor and the resistor for any loose connections, corrosion, or broken wires. Clean and tighten any loose connections.
5. Check the Blower Motor Relay: Locate the relay (your owner's manual should indicate its location and identification). You can often swap it with a similar-looking relay (check the amperage rating) to see if that resolves the issue.
6. Test the Blower Motor: This requires more advanced testing (multimeter) and potentially removing the blower motor from its housing to test its functionality directly. This is best left to someone with electrical experience.
7. Control Panel: If other steps don't work, the control panel itself could be the culprit.
Important Notes:
* Safety First: Disconnect the negative battery terminal before working on any electrical components.
* Consult a Repair Manual: A repair manual specific to your 2004 Jeep Grand Cherokee will provide detailed diagrams and instructions.
* Professional Help: If you're uncomfortable working on your vehicle's electrical system, it's best to take it to a qualified mechanic.
By systematically going through these steps, you should be able to narrow down the cause of the problem and get your Jeep's fan blowing again. Remember to replace parts with OEM (Original Equipment Manufacturer) parts whenever possible for the best results.
