I have my second 1999 as class Mercedes and both have the same problem. The door assist system stop working on the passenger door in the trunk. The only way to get it working again is to remove the fuse associated with that system and reseat it. Does anyone have a better solution for this?
I worked at a Benz dealer for many years, and I’m quite familiar with your car.
The best and cheapest solution is to just live with it.
The more expensive solution is to replace the PSE pump . . . the pneumatic systems equipment pump, located in the trunk.
If it was my car, I’d just live with it and slam any doors closed which didn’t close with assist.