1. Check the Easy Stuff First:
* AC Switch: Make sure the AC is actually turned ON in the cabin. Sometimes it's accidentally switched off.
* Fan Speed: Is the fan speed set to a position other than "OFF"? Try adjusting the fan speed.
* Blown Fuse: Check the fuses related to the AC blower motor and its circuit. Your owner's manual will show you the fuse box location and the fuse diagram.
* Low Refrigerant: A low refrigerant level can cause the compressor to cycle on and off erratically, potentially affecting the fan. This would be accompanied by weak or no cold air. A mechanic needs to check this with specialized equipment.
2. More Involved Troubleshooting:
* Blower Motor Resistor: This component controls the fan speeds. A faulty resistor can cause the fan to stop working altogether or only work on high speed (if at all). This is a common failure point. Replacement is relatively inexpensive but may require some mechanical skill.
* Blower Motor: The motor itself could be failing. This is less common than a bad resistor but still possible. Testing requires multimeter skills.
* Wiring and Connections: Check all wiring and connections to the blower motor, resistor, and related components for corrosion, damage, or loose connections.
* Control Module (often called the HVAC control module): This is the electronic brain of the climate control system. A failing control module can cause various malfunctions, including the fan stopping. This is a more expensive repair, often requiring professional diagnosis.
* Relay: The AC fan may be controlled by a relay. A faulty relay can prevent power from reaching the fan.
3. Getting Help:
* Owner's Manual: Consult your owner's manual for diagrams, fuse locations, and troubleshooting information specific to your vehicle.
* Online Forums: Search online forums (like Dodge Ram forums) for similar issues with your model year and engine. Someone else may have experienced the same problem and found a solution.
* Mechanic: If you are uncomfortable troubleshooting electrical issues, take your truck to a qualified mechanic. They have the tools and expertise to diagnose the problem accurately.
Important Note: Before working on any electrical components, disconnect the negative battery terminal to prevent accidental shorts and injury.
Start with the simplest checks (fuse, switch, fan speed). If those don't resolve the issue, then systematically investigate the other possibilities. If you're not comfortable with electrical work, it's best to seek professional help.
