One of great features S-class Mercedes Benz has is door and trunk closing assistance. Once door is latched and trunk pushed to close electric pump pulls it in. As vehicle ages many pumps start failing leaving owner slam doors and trunk to close them fully. Trunk, however, will be the hardest to slam and once closed there will be a gap between trunk and car body. All that is caused by faulty close assist pump.
In most cases drivers door fails to close itself first as it’s used the most. Many people reset pump by pulling the fuse #9 out trunk fuse panel. After some time pump stops operating again because the problem is not repaired with reset. There are few things that can go wrong: vacuum leak inside door or trunk close assist mechanism, leaking vacuum connections on pump or actuators, leaking vacuum hose, pump out the adjustment internally, pump valves leaking, shut off valve leaking, and pump motor blown if pump doesn’t run at all.
In most cases if one of the doors or trunk stop working but rear doors still work pump pressure needs adjusting. I can adjust the pressure in your pump and test it on my own car to make sure there are no internal failure in the pump. That is first step in troubleshooting close assist system. I make videos of testing pump on my car so you will be certain that after you receive it back and if there are any other issues with system pump can be ruled out.
Pump adjustment is $200 plus shipping. If your pump stops operating after every fuse #9 reset then you might have other pump failure and simple adjustment might not fix it. Let me know your symptoms and we can take it from there.
Below is the video of customers pump testing on my car