1. Low System Pressure:
* Even with freon, pressure switches are crucial. The low-pressure switch and/or high-pressure switch prevent the compressor from engaging if the pressure is too low or too high to protect the system. A leak, even a small one, can cause low pressure. A clogged orifice tube or expansion valve can also cause low pressure. You need gauges to check the pressure. Don't just assume you have enough freon.
2. Cycling Switch (or Pressure Switch):
* These switches are safety devices. If they're faulty, they might not allow the compressor to engage even with adequate freon. These switches can be tested with a multimeter, or replaced as a relatively inexpensive part.
3. Clutch Relay:
* The compressor clutch is electromagnetic. A faulty relay prevents power from reaching the clutch, and thus the compressor won't engage. You can test this by swapping it with a known good relay of the same amperage rating (check your owner's manual or a wiring diagram).
4. AC Compressor Clutch:
* The clutch itself might be faulty. It could be seized, worn out, or have a damaged coil. Testing the clutch coil resistance with a multimeter might identify this as the problem. Often, a failed clutch coil will manifest as no engagement and a clicking sound.
5. Blower Motor Relay and Fuse:
* While not directly connected to the compressor, the blower motor has to be on for the system to run (often in "high" fan speed). A faulty relay or blown fuse will prevent the blower from operating, and therefore the compressor will not turn on. Check these first.
6. Wiring and Connections:
* Inspect all wiring and connectors related to the AC system. Look for corrosion, loose connections, or broken wires. A simple wiring issue is a possibility.
7. Compressor Itself:
* In rare cases, the compressor itself might be bad. This is less likely if the clutch isn't engaging, but it's possible. You would need to rule out all other issues first.
8. AC Control Panel/Module:
* A faulty AC control panel or module can prevent the compressor from turning on. This is a less common cause, but possible.
What You Should Do:
1. Check the fuses and relays: This is the easiest and cheapest place to start.
2. Check the pressure: You'll need AC gauges to do this properly. Low pressure is a very common cause of the compressor not turning on. If the pressure is low, there's likely a leak, or a restriction in the system.
3. Consult a wiring diagram: This will help you trace the wiring and test components systematically. You can often find these diagrams online.
4. Consider professional help: If you're not comfortable working with automotive electrical systems or AC refrigerant, it's best to take your Windstar to a qualified mechanic. Improper handling of refrigerant can be dangerous.
Remember, working with automotive AC systems requires specialized tools and knowledge. Improper handling of refrigerant can be harmful to you and the environment. If you're unsure about any step, seek professional help.
