* Electrical Issues: This is the most likely culprit. Check these:
* AC Compressor Clutch Relay: This relay controls power to the compressor clutch. A bad relay prevents the compressor from engaging. Test the relay with a multimeter or replace it as a cheap troubleshooting step.
* Low Pressure Switch: This switch prevents the compressor from turning on if the system pressure is too low (even if the system is fully charged, a leak elsewhere could cause this). A faulty switch can prevent the compressor from engaging even with sufficient refrigerant.
* Blown Fuse: Check the fuse related to the AC system in the fuse box.
* Wiring: Inspect the wiring harness leading to the compressor and other AC components for damage, shorts, or loose connections. A break in the wire is a common problem in older cars.
* Cycling Switch: Some systems have a cycling switch that controls when the compressor is on and off based on temperature. A problem here will prevent the compressor from starting.
* System Leaks (despite a recent charge): Despite a recent charge, there might still be a slow leak somewhere in the system. A leak would eventually deplete the freon. You need a leak detection test to confirm this. The leak may be difficult to find and even a tiny hole can render the system ineffective.
* Bad Compressor Clutch: Even a new compressor *could* have a faulty clutch. Although less likely given the compressor is new, it's worth considering if the electrical checks pass. The clutch could be failing to engage properly.
* Incorrect Refrigerant Charge: While you say it's fully charged, the *type* and *amount* of refrigerant might be incorrect. Overcharging can also damage the system. A properly calibrated gauge set is crucial for accurate charging.
* Problems with the Expansion Valve (orifice tube): While you replaced it, there's a chance the new orifice tube is defective or improperly installed. This could restrict refrigerant flow.
* Blower Motor Issues: Although this won't prevent the compressor from running, a malfunctioning blower motor means no cool air will reach the cabin, even if the compressor is working.
Troubleshooting Steps:
1. Start with the easiest: Check the fuse and relay first. These are cheap and easy to replace.
2. Electrical Tests: Use a multimeter to test the power supply to the compressor clutch and the low-pressure switch.
3. Leak Detection: Use a dye or electronic leak detector to find any small leaks in the system.
4. Pressure Check: Verify the system pressure using gauges (this needs to be done by someone who knows how to use the gauges properly).
5. Compressor Clutch Test: Manually try to engage the compressor clutch (be careful not to get injured). If it doesn't engage easily, it might be faulty.
If you're not comfortable working on car AC systems, it's best to take your DeVille to a qualified automotive air conditioning specialist. Improper handling of refrigerants can be dangerous.
