1. Check the Blends and Controls:
* Rear AC Controls: Make absolutely sure the rear AC is actually turned *on* and set to a cool temperature. Seems obvious, but it's the easiest thing to overlook. Many Expeditions have separate controls for rear climate. Check for any fuses related specifically to the rear AC.
* Mode Selector: Ensure the mode selector (usually a dial or buttons) is set to blow air to the rear. If it's set to "front" or "off," no air will go to the rear.
* Temperature Control: Verify the rear temperature isn't set too high.
* Fan Speed: Make sure the rear fan isn't set to zero.
2. Check the Rear Blower Motor:
* Listen for the Motor: With the rear AC on, listen carefully near the rear of the vehicle. Can you hear the blower motor running? If not, it could be faulty, have a blown fuse, or a bad switch.
* Access the Blower Motor: Locate the rear blower motor (usually under the rear seats or in the cargo area). Accessing it might require removing panels. Once located, visually inspect it for any obvious damage. You can try manually spinning the blower motor shaft; it should spin freely.
* Test the Blower Motor (Advanced): You may need a multimeter to test the blower motor's power supply and resistance to confirm if it's receiving power and if the motor itself is functioning correctly.
3. Check the Rear Evaporator:
* Frozen Evaporator: A frozen evaporator core means restricted airflow and no cold air. This is often caused by a lack of airflow or a refrigerant leak, even if the front AC works. This is more likely if you *hear* the blower motor running.
* Access: Accessing the rear evaporator is more difficult and usually requires removing significant interior panels. This should only be attempted if you're comfortable with automotive repairs.
4. Check the Rear AC Lines and Connections:
* Leaks: Visually inspect the rear AC lines for any visible signs of leaks (oil stains or refrigerant).
* Connections: Check all connections for tightness and corrosion.
5. Refrigerant Levels (Least Likely but Possible):
While less likely if the front AC works, a *small* refrigerant leak confined to the rear lines is still possible. However, if the front AC is properly chilled, this is lower on the list. This requires professional AC service equipment.
6. Professional Help:
If you've gone through these steps and are still stuck, it's best to take your Expedition to a qualified automotive AC technician. They have the tools and experience to diagnose and repair more complex issues, like electrical problems, clogged lines, or refrigerant leaks that may be subtle. They can also perform a pressure test to check the refrigerant levels in the rear system specifically.
Remember safety first! Disconnect the battery before working with any electrical components. If you're not comfortable working on your vehicle's AC system, don't hesitate to seek professional help to avoid further damage or injury.
