Greetings to everybody,
I am a newcomer to this community and I own a very intricate problem, necessitating an extensive post to provide context on the origin of the issue. Therefore, please be patient with me.
I own a 2007 Mercedes W221, which I am really satisfied with, and I have maintained it meticulously. It is outfitted with the M273 E55 engine.
Approximately eighteen months ago, all four struts and shock absorbers malfunctioned. There was a break of many days between each strut collapse, nevertheless they ultimately failed. I replaced them with original refurbished units that with a guarantee. This constitutes error number one.
Since installing these struts, a yellow malfunction message has shown on my dashboard, accompanied by a picture of an automobile with an upward-pointing arrow.
The struts were changed many more times throughout that eighteen-month period due to the car's sagging issue. The last modification included the replacement of the two rear struts, which were incapable of maintaining pressure (still under warranty). The rear struts now support passengers well; nonetheless, the ride comfort is subpar. The journey is jarring, rigid, and I could perceive the gravel on the roadway.
Recently, I opted for a do-it-yourself approach to address the problem independently, given the exorbitant cost of fixing the AirMatic system at a skilled mechanic. I elevated the vehicle using a floor jack and positioned jack stands underneath it. Removed the front wheels and wheel wells to provide access to the valve block, compressor, reservoir, and other components. I prepared a solution of soapy water and applied it to the connections of the air lines to the struts from above, both at the front and back of the vehicle, and activated the lift car button inside the cabin to pressurize the system. No bubbling occurred. I attempted to detect hissing (escaping air) with an automobile stethoscope, but found no evidence. I applied soapy water to the connections of the valve block, compressor, and reservoir, and to my astonishment, there were no leaks or hissing sounds. I concluded that the struts are functioning properly; nevertheless, the lines must be the problem, since a diagnostic scan at a mechanic's shop revealed an error indicating that the reservoir took too long to achieve the appropriate pressure. This validates the existence of a leak. I decided to inspect the fuse box (N10/1) located in the engine compartment. Two relays are designated for the air pump and the air compressor. N10/1kA, which designates relay A, is responsible for the air pump. N10/1kB denotes relay B, which is responsible for the air suspension compressor.
I extracted these two relays and using a gadget designed to test them by plugging them in; a clicking sound indicates regular functionality. That is the occurrence that transpired. Upon returning the relays to their designated positions, I subsequently observed that the front of the vehicle sagged, allowing just a single finger to pass between the wheel and the fender, in contrast to the prior clearance of 2-3 fingers. Additionally, the compressor ceased functioning, even under stress on the struts. The lift vehicle button is inoperative; it is either fixed in the "on" position or the "off" position, indicated by a red light next to the button. The activation of this button is contingent upon the speed at which I push it immediately after starting the automobile. Irrespective of the switch's position, the compressor fails to activate. I am now perplexed; what transpired? It functioned properly prior to my removal of the relays.
I presumed that the relays were defective, so I procured two relays (N10/1kB) from the scrapyard, verified their functionality, replaced the old relay with a new one, but was unsuccessful. I replaced both the N10/1kA relay and the N10/1kB relay with other relays inside the same fuse box to see if it would resolve the issue, however this approach was similarly ineffective. I now own not just a defective airmatic system but also an inoperative compressor.
I consulted a technician at MB for his assessment on this issue; he advised testing the air lines for integrity and any leaks. He recommended that I get four new airlines, link them to the valve block, and detach the existing air lines from the struts and attach the new ones. Two air lines connect the engine compartment to the front struts, while two air lines extend through the back window to the rear struts to pressurize the system. Subsequently, leave the vehicle overnight and see if it sags. If sagging occurs, the preceding lines are acceptable, and it is likely indicative of a leak in the compressor, valve block, or reservoir. If there is no leakage, the old air lines must be replaced, or at the very least, identify the leaky air line and repair that specific section. The replacement is labor-intensive and expensive, since it necessitates the substitution of the complete assembly if the leak occurs in the center of the air line, where access is limited. He further said to either repair the relays for the compressor or, if necessary, replace the complete compressor due to potential failure. However, the inquiry is if I may circumvent the fuse box and directly connect 12V from the battery to the compressor to see whether it activates. Despite the absence of constraints on current? Would that entirely obliterate it?
I measured the voltage at each pin in the relay socket, and it seems to be malfunctioning. While the vehicle is operational, pin 85 or 86 is expected to be grounded at 0 volts; yet, it inexplicably registers slightly over 12 volts. I must re-evaluate this, since it is inconsistent.
It is noteworthy that during my examination of the air lines from the compressor, I saw that an air line originating from the valve block is secured with a zip tie and exhibits abrupt bends at two distinct points. I can see that the line is under tension, and when placing my finger behind it, I detected pronounced grooves precisely at the point of curvature; yet, I am unable to visually inspect it due to its inaccessibility. Uncertain if it is only debris or whether the air line is indeed compromised, perhaps causing the airmatic failure; nonetheless, I have seen a similar configuration in many other YouTube films on this topic.
The compressor emitted a regular sound during operation, indicating it was not malfunctioning. The automobile emits a pronounced WHOOSH when I shut the door and secure it, as if expressing irritation. This occurs mostly when I return after a drive. I assume it is alleviating pressure from the struts. The height level sensors are not misaligned, hence I do not believe they are providing erroneous results. I also detect a subtle, prolonged medium-pitched beep emanating from the engine compartment. It may signify the conclusion of a process or the breakdown of a process within its systems. The primary battery in the engine compartment is neither from Mercedes nor Bosch; I have been informed that using a different brand disrupts the vehicle's electronics, as shown by the current issues with the relays. Please confirm.
Your insights on this matter would be greatly valued, as the vehicle is currently immobilized before me. If I attempt to drive it, it will eventually emit a warning indicating "car too low," due to the compressor failing to activate and thus unable to restore the lost pressure. This will result in the car becoming a low rider, potentially causing internal fender scraping during turns or movement. I apologize for the lengthy discussion, but these two problems are troubling me, and I really like driving this vehicle.
The vehicle was elevated on jack stands with the battery disconnected for ten days previous to this situation, since I had gone on holiday. This is to prevent returning to a low rider and incurring expensive repairs or replacements of all four struts. To prevent the self-leveling mechanism from disrupting the configuration or returning to a depleted battery.
