What a height sensor does
It's a small sensor bolted to the body with a little link rod running down to the suspension arm. When the suspension moves, the rod twists the sensor, and the sensor tells the computer exactly how high that corner is sitting. The computer then adds or dumps air to hit its target height.
So the whole air suspension is only as honest as these four little sensors. The computer can't actually see the car — it just believes whatever they tell it. Keep that in mind, because it explains everything that follows.
I match the VIN, exact corner, arm orientation, connector and mounting. Before shipment I confirm whether calibration or ride-height relearning is required after fitting.
OE / VIN · FITMENT · TEST · WARRANTYThe computer can't see the vehicle. It only knows what the height sensors tell it.
What happens when one lies
Exactly what you'd guess, and it looks just like a suspension fault. If the sensor reads lower than the truth, the computer keeps pumping air in — and that corner ends up jacked too high. If it reads higher than the truth, the computer keeps letting air out — and the corner squats too low. Nothing's leaking. Nothing's broken. The system is faithfully obeying a lie.
You might also get warning messages, a car stuck in one height, or one that flat refuses to lift for a rough road.
Telling it apart from a leaking spring
Here's the check that saves an expensive mistake. A leaking spring sinks slowly overnight and pumps back up in the morning — it's a story about time. A bad height sensor gives the wrong height the instant you look, and keeps on giving it. No overnight drop, because there's no leak.
So if a corner's wrong the moment you walk up to it and stays wrong, stop hunting for leaks and look at the sensor and its little link rod.
Why they fail
They live underneath the car in the water, salt, sand and stones, moving constantly. The insides wear or corrode. The sensor is not the only possibility; the link rod and its ball joints are also frequent causes. A snapped, seized or popped-off link rod means the sensor can't feel the movement, and you get the exact same symptoms. Inspect the linkage before condemning the sensor. It's often a two dollar fix, not a much larger repair.
What to order — and the step everyone forgets
Two things. First, position: front left, front right, rear left, rear right are often different part numbers with different rod lengths and plug angles. Send the VIN and say which corner. Second — and this catches people out — on most cars the system has to be recalibrated after you fit a height sensor, with a scan tool, to teach the computer the new sensor's zero point. Skip that and the ride height's wrong, and your part cops the blame for a fault it doesn't have.
What I check before shipment
I match the VIN, exact corner, arm orientation, connector and mounting. Before shipment I confirm whether calibration or ride-height relearning is required after fitting.
Diagnosis and safety note
This guide describes common failure patterns, not a final diagnosis. Confirm fault codes, live data, wiring, fitment and the vehicle-specific service information before ordering or fitting a part. Safety-critical, refrigerant, high-pressure and drivetrain work should be handled by a qualified technician using the correct procedures.
Frequently asked questions
Can you just adjust the link rod to fix the height? People do, and it's a bad idea — it hides a sensor fault and throws off the geometry the whole system was set up around. Calibrate it properly instead.
New sensor, height still wrong — why? Check calibration, linkage condition, wiring, exact corner and the correct part number before deciding the new unit is faulty.
Do they need doing in pairs? No — unlike springs, these fail one at a time. Replace the bad one and calibrate.
Need height sensors and air suspension parts?
I supply height sensors, air springs, compressors and valve blocks for Range Rover, Mercedes, BMW and Audi out of China — matched to your VIN and the corner, tested, with warranty. Small or mixed orders welcome, and the sensors are easy to consolidate into a mixed shipment. Send me the VIN on WhatsApp and I will confirm fitment, testing, warranty and shipping options before you order.