* Blend Door Actuator/Cable Issues: This is a common problem. The blend door controls the direction of airflow (dash, floor, defrost). If the actuator (electric motor) or cable (mechanical system) is broken or jammed, it can prevent air from reaching the dash vents. You might find air coming out of the floor or defrost vents, but not the dash.
* Blower Motor: The blower motor is responsible for pushing air through the system. If it's failed, you'll get no airflow at all, regardless of the AC or vent settings. Listen carefully – you should hear a whirring sound when the fan is on.
* Blower Motor Resistor: This component controls the fan speed. A faulty resistor can prevent the blower motor from working altogether, or only at one speed (often high). This is less likely to completely prevent air, but it's possible.
* Vacuum Leaks: Many older cars, including some Mustangs, use vacuum to control some aspects of the climate control system, including the blend doors. A leak in the vacuum lines can prevent proper operation.
* Fuse: A blown fuse related to the blower motor or AC system will stop airflow completely. Check your owner's manual for the relevant fuses.
* AC Compressor Clutch: While the AC being on won't directly force air out of the vents, a non-functioning compressor means no cold air, but it shouldn't stop *air* flow completely unless something else is also wrong (like a low refrigerant level). It's less likely to be the *sole* cause of no airflow from the dash vents.
* Refrigerant Level: As mentioned above, low refrigerant will prevent the AC from cooling, but air should still flow. However, a severely low level *could* cause issues in some systems, especially if it triggers a safety switch.
* Stuck or Blocked Vents: Check the vents themselves to ensure they aren't clogged with debris.
Troubleshooting Steps:
1. Check the fuses: Start with the easiest check.
2. Listen for the blower motor: Can you hear it running at all? If not, suspect the motor or resistor.
3. Check the fan speed selector: Does changing the fan speed setting have any effect?
4. Try different vent settings: See if air comes out of the floor or defrost vents. This helps isolate whether it's a blend door issue.
5. Inspect the vacuum lines (if applicable): Look for any obvious cracks or damage.
6. Visually inspect the vents: Are they blocked?
If you're not comfortable working on your car's electrical or HVAC system, it's best to take it to a mechanic. Diagnosing this problem can require specialized tools and knowledge.
