The Presenting Situation
The car arrived with the left rear sitting approximately three inches lower than the other three corners. The owner had noticed it developing slowly over two weeks — one morning it would look normal, the next it would be low again, then eventually it stopped correcting itself entirely. The AIRMATIC warning hadn't illuminated yet. The owner assumed it was one strut and wanted a quote for replacing the left rear air strut.
That instinct was reasonable. One corner sitting low is almost always a leaking strut on that corner. But "almost always" isn't "always," and a complete AIRMATIC diagnosis — not just a visual inspection and a quote — is the right starting point on any AIRMATIC complaint.
What XENTRY Showed
Connected to XENTRY, the AIRMATIC module reported three stored faults: left rear height sensor reading below minimum, compressor motor current draw above threshold (indicating the compressor was running longer than normal to maintain pressure), and a valve block solenoid fault on the left rear circuit. The compressor fault was stored, not active — meaning the compressor had been overworking but hadn't failed yet. The solenoid fault indicated the valve block controlling air routing to the left rear was functioning at the edge of its specification.
The height sensor data confirmed the left rear strut had been slowly deflating. The compressor data confirmed what you'd predict — it had been compensating for weeks, running overtime, and the motor was beginning to show the wear of that extended duty cycle.
The Complete Diagnosis
Based on the XENTRY data, the correct repair was: left rear air strut (confirmed leaking), valve block replacement (solenoid fault indicated imminent failure, and failure of the valve block after a new strut installation would immediately stress the new strut and the already-compromised compressor), and compressor inspection with a recommendation to replace preemptively given the stored overload history. Optionally: a leak-down test of all four struts to establish baseline health on the other three corners.
The "one strut" approach the owner initially expected would have cost $650–$800. The correct repair came to $2,400. That's a real and significant difference. But it's also the repair that would restore the system to genuine health, not patch the most visible symptom while leaving a weakened compressor and a marginal valve block in place.
How to Present This to an Owner
The conversation with the owner covered exactly this: yes, the left rear strut is what's causing the car to sit low right now. But the XENTRY data shows the compressor has been overworking for weeks in response to that strut leak, and the valve block on that circuit has a stored fault that suggests it's failing. If we replace just the strut and the compressor fails in three months, we're back in here for another repair event that costs more than doing it correctly now — and you've paid for strut labor twice. The owner understood the logic and authorized the complete repair.
The Takeaway for AIRMATIC Owners
AIRMATIC is a system — not a collection of independent components. When one part of the system fails, the other parts respond to compensate. A leaking strut doesn't fail in isolation; it stresses the compressor, potentially stresses the valve block, and changes the pressure cycling behavior the entire system was calibrated around. Diagnosing only the presenting symptom misses the system-level consequences of that symptom.
This is the core reason a complete XENTRY diagnostic is the correct first step for any AIRMATIC complaint — not a visual inspection, not a quote for the obvious part, but a full module-level scan that tells you what the system has been experiencing, not just what it's doing right now. The full diagnostic background is in the AIRMATIC failure guide.