1. Blower Motor Resistor: This is the most frequent cause. The resistor controls the fan speeds. If it fails, you'll lose all fan speeds, including the highest. It's relatively inexpensive and easy to replace (usually located under the dash).
* How to check: Visually inspect the resistor for burn marks or obvious damage. A multimeter can test for continuity, but this requires some electrical knowledge.
2. Blower Motor: While less common than the resistor, a failed blower motor itself can cause a complete loss of fan function. It's located behind the glove box or under the dash, depending on the exact model.
* How to check: You'll likely need to access the motor. You can try tapping it gently while someone turns the fan on; a faint whirring sound might indicate a failing motor. Testing with a multimeter is also possible but requires electrical knowledge.
3. Fuse: Check the fuses related to the blower motor and AC system in the fuse box (usually under the hood and/or inside the cabin). A blown fuse is a simple and cheap fix.
4. Relay: Similar to a fuse, a relay can fail and cut power to the blower motor. These are usually located in the underhood fuse box or a separate relay center. A visual inspection for damage is a good starting point. You can swap relays with a similar one (same amperage rating) to see if that resolves the issue, but be careful.
5. Wiring/Connectors: Check the wiring harness leading to the blower motor and resistor for any loose connections, broken wires, or corrosion. This can be tricky, often requiring removal of parts to access the wiring thoroughly.
6. Blower Motor Control Module (Less Likely): This is less common but possible. The control module regulates the blower motor speed. A faulty module usually results in erratic behavior or complete failure. Replacement is generally more expensive.
7. AC System Issues (Less Likely if Heater is also out): While unlikely to cause a complete loss of blower function, a major problem within the AC system (like a failed compressor clutch) *could* indirectly affect the blower (though the heater should still work).
Troubleshooting Steps:
1. Check the fuses and relays first. This is the easiest and cheapest thing to do.
2. Inspect the blower motor resistor. This is often the culprit.
3. If the resistor is fine, check the blower motor. Accessing this might be more difficult.
4. Inspect wiring and connectors for damage or loose connections.
5. If all else fails, consider taking your Durango to a mechanic. They have the tools and expertise to diagnose the problem more accurately.
Remember to always disconnect the negative battery terminal before working with any electrical components in your vehicle. If you are not comfortable working with automotive electrical systems, it's best to seek professional help.
