1. Safety First: Before you start, make sure the car is parked on a level surface, the engine is off, and the parking brake is firmly engaged. Air suspension systems operate under pressure, so be cautious.
2. Visual Inspection:
* Leaks: Carefully inspect the air springs themselves for any visible leaks. Look for cracks, tears, or worn areas around the connection points. Use soapy water to check for air leaks; bubbles will indicate a leak.
* Hoses and Fittings: Examine all the air lines and fittings connecting the air springs to the compressor and valve system. Look for cracks, loose connections, or signs of damage.
* Compressor: Locate the air compressor (usually under the hood). Listen for any unusual noises (whining, grinding) when you try to raise the suspension. Visually inspect it for obvious damage.
3. Testing the System:
* Check the Suspension Height: With the engine running, does the rear end raise to the normal ride height? If not, there's a problem.
* Operate the Ride Height Control (if equipped): Some DeVille models had a switch to manually adjust the ride height. If your car has this, try using it to see if the rear end responds. No response points to a problem in the system.
* Listen for the Compressor: When you try to raise the suspension, can you hear the compressor running? If not, the compressor might be faulty, or there's an electrical problem.
* Listen for Air Leaks: With the engine running and trying to raise the suspension, listen closely near the air springs. You might hear a hissing sound if there's a leak.
* Check the Fuses/Relays: Check the fuse box (usually under the hood or inside the car) for any blown fuses related to the air suspension system. Also, inspect any relays associated with the system.
* Diagnostics (Advanced): You may need a diagnostic scanner that can read codes from the car's computer. This will give you specific trouble codes that can point to the faulty component (e.g., compressor failure, sensor malfunction, valve block problem). A professional mechanic would likely use this tool.
4. Focusing on the Switch and Pump (Compressor):
* Switch: If you have a manual ride height control switch, test its continuity with a multimeter (if you have one). If the switch is bad, it won't send the signal to the air compressor. However, this is less common than other components failing.
* Pump (Compressor): If the compressor isn't running or is making unusual noises, it's the most likely suspect. This often requires replacement. You could try temporarily bypassing the switch to see if the compressor runs (this requires understanding the electrical wiring—don't do this unless you're experienced with automotive electrical systems).
5. Getting Help:
* Professional Mechanic: If you're not comfortable with automotive repair, take your Cadillac to a qualified mechanic. They have the diagnostic tools and expertise to accurately identify and fix the problem. Air suspension systems can be complex.
* Online Forums: Search online Cadillac forums (e.g., Cadillac forums on dedicated automotive websites). Other DeVille owners may have encountered similar issues and can offer valuable insights.
Important Considerations:
* Age and Wear: Air suspension components wear out over time. The compressor, air springs, and other parts are susceptible to failure after many years of use.
* Repair vs. Replacement: Repairing some components might be possible, while others (like a severely damaged air spring or compressor) might require replacement. Replacement parts can be relatively expensive.
By systematically checking these points, you should be able to narrow down the cause of your rear air shock issues. Remember, safety is paramount, so proceed cautiously and seek professional help if you're unsure about any step.
