1. Low Refrigerant:
* Why: This is the most common reason for intermittent hot air. Even a small leak can cause the system to cycle on and off as the refrigerant pressure fluctuates.
* How to check: A qualified mechanic needs to check the refrigerant pressure using gauges. Don't try this yourself unless you have experience with automotive AC systems – improper handling can expose you to harmful refrigerants.
2. Cycling AC Compressor:
* Why: The compressor might be failing, only engaging intermittently. This could be due to a failing clutch, low refrigerant (as mentioned above), or a problem with the compressor itself.
* How to check: Listen carefully for the compressor to engage (a clicking sound from the compressor clutch and a change in engine sound) when the AC is turned on. If it cycles on and off rapidly or doesn't engage consistently, this is a likely culprit.
3. Pressure Switch/Sensor Problems:
* Why: A faulty pressure switch or sensor can cause the system to shut down prematurely if it reads incorrect pressure levels.
* How to check: This requires a mechanic with diagnostic equipment to check sensor readings.
4. Electrical Issues:
* Why: A short circuit, bad wiring, or a failing control module (other than the blend door actuator you replaced) could interrupt power to the AC compressor or other components.
* How to check: A mechanic with a multimeter can check for voltage and continuity in the AC system's wiring.
5. Evaporator Problems:
* Why: A restricted or clogged evaporator core (located inside the dashboard) can hinder airflow and cause inconsistent cooling.
* How to check: This typically requires professional inspection and often involves removal of parts of the dash.
6. Condenser Problems:
* Why: A dirty or damaged condenser (located in front of the radiator) restricts airflow and reduces cooling efficiency.
* How to check: Visually inspect the condenser for debris or damage. Cleaning it might help, but a severely damaged condenser needs replacement.
Recommendations:
* Start with the refrigerant check: This is the easiest and most likely culprit for intermittent cooling issues. A mechanic can quickly determine if this is the problem.
* Professional Diagnosis: Given that you've already replaced a component, further troubleshooting requires specialized tools and knowledge. Taking your Windstar to a qualified mechanic specializing in automotive AC systems is strongly recommended. They can perform a proper diagnostic test to pinpoint the exact problem and provide the most effective solution. Guessing and replacing parts without a proper diagnosis can be costly and time-consuming.
Ignoring a failing AC system can lead to further damage, so it's best to address the issue promptly.
