* Blend Door Actuator: This small motor controls the direction of the airflow (dash vents, floor vents, defrost). If it's malfunctioning, it might be stuck in a position that prevents cold air from reaching the dash vents, even if the compressor is working and the rear AC is fine. This is a very common problem on older vehicles.
* Vacuum Leaks: The blend door actuator is often controlled by vacuum lines. Leaks in these lines can prevent proper operation of the blend door, again leading to no cold air at the dash.
* Dash Vent Actuator: Some Windstars have separate actuators for each dash vent. A malfunctioning one could restrict air to a specific dash vent or prevent all dash vents from working.
* Blocked Dash Vents: It's possible something is blocking the airflow within the dash vents themselves – leaves, debris, etc.
* Low Refrigerant (Less Likely): While less probable given the rear AC works, a slight refrigerant leak *could* affect the dash system more significantly than the rear system, though this is unlikely. A significant leak would impact both.
* Faulty AC Amplifier (or similar control module): The vehicle's control system might be faulty and not sending the signal to engage the front AC system. This requires more electrical diagnostic work.
Troubleshooting Steps:
1. Check the blend door controls: Manually switch between defrost, floor, and dash settings. If you hear no motor sounds (or unusual sounds) from the HVAC unit during switching, the blend door actuator is a prime suspect.
2. Listen for unusual noises: When the AC is running, listen carefully near the HVAC unit for unusual noises that could indicate a malfunctioning actuator or vacuum leak.
3. Inspect dash vents for blockages: Ensure nothing is obstructing airflow.
4. Check vacuum lines (advanced): This requires some mechanical knowledge and might involve removing parts to inspect lines visually.
Recommendation:
Unless you have experience with automotive AC systems, it's best to take your Windstar to a qualified mechanic. Diagnosing the issue accurately can be tricky, and improper handling of refrigerant can be dangerous. The mechanic will have the tools and expertise to quickly pinpoint and fix the problem efficiently.
