soft close trunk lid

A note on trunk lift cylinders

 the 2 lift cylinders that hold the trunk open are part number A230 750 00 36 

the cheapos are just that, only last a couple of years, and often are the wrong pressure... bought genuine mercedes parts this time.

You want these functioning properly BEFORE working on the latching mechanism, due to how the system understands to operate the soft close mechanism.

The soft close operation

 The SL has a "soft close" feature, where when closing, the mechanical latch is between the lid and the body is first engaged, and then the system pulls the lid all the way closed

the last bit of closure is accomplished by vacuum, the system that also moves the door locks.

If there are issues, the first thing to check is remove and replace the fuse, which is in the bottom of one of the 2 storage compartments behind the seats, the one that does not have the CD changer.

You can remove the floor of the bin by very gently pulling back on the tabs which are at the back of the bin and lifting. Be careful, if you overdo it, you will break the tabs.
You can then reach in and push the vertical trim plate at the front out from behind. You’ll then see the fuses, the one you want is yellow, 20A, about 3 or 4 over from the left. If the fuse is blown, replace it with a new one, otherwise just plug the fuse back in. You should hear the PSE pump in the trunk run for a short while. You can then check the individual functions, central locking, trunk lid soft close, massaging seats if you have them.

The pneumatic pump in the trunk shuts down this function if a leak or other problem is detected. It’s a very common problem and the first thing to try is removing the yellow 20A fuse in the fuse area under the storage boxes and replacing it. This erases the pump memory so that it will re-enable the soft close. (the better way to do this is to use a scan tool to read and reset the fault)

The door locks, the fuel filler cap lock, the storage compartments behind the seats and massaging seats are also pneumatically controlled/ocked. The is all from the pump on the bottom of the "stack" in the trunk. The top pump is the hydraulic pump for the Vario top.


If the pump runs on after the soft close, you may well have a leak somewhere. If nothing works, it’s likely the pump has failed, it uses a graphite rotor which is quite fragile.

Normally there is a leak in the soft close mechanism, here is a good video showing the potential leak areas, and how to fix.


Fuse F71 for the pump

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