rainerk1974

Hello everyone.
I'm new to this forum, and maybe someone has presented this problem before, but I couldn't find anything when searching the forum.

Last year the light on the trunk release switch on the center console started going on even if the trunk was closed, and that means that I can't get the roof down. The problem came and went a few times and I had the car looked at by a dealership. They replaced a wire and told me that if that didn't help I had to replace the whole trunk lock mechanism. Now the light stays on all the time, and as replacing the lock mechanism is pretty expensive I wonder if someone knows if there is a possibility to bypass/short circuit the trunk sensor/trunk release switch so that I can operate the roof again?

I would be grateful for any help/answers.

burgca

https://mbworld.org/forums/clk-class...ght-stays.html

burgca

https://mbworld.org/forums/clk-class...ailures-3.html

Serndipity

When the lamp on the center console trunk release switch is on, it indicates that the truck is in an unlocked condition. By design, to prevent a potential collision between the soft top case cover and truck lid, the roof's controller (N52) will be notified of this condition, by the interior CANBus.

Although the N52 controller talks with the CANBus network, using only 2 of it's 55 wiring connections (e.g. CAN-Data-Bus HIGH and LOW), there is not a way to restore your power roof operation without correcting the problem current fault (e.g. the N52 controller thinks the truck is unlocked).

Tha'is because the CANBus; uses both a physical (e.g. twisted wire pair and voltage encoding), as well as a protocol based data layer, to communicate with it's numerous network connected nodes/device-controllers and prior to permitting power roof operation, the N52 controller will first verify that all other prerequisites are correct (e.g. vehicle speed not more than a specified MPH, the truck is not unlocked, the window have opened etc.).

Included below, is a functional diagram of trunk locking system, it's components and the methods used to interact.

Before replacing expensive components, some additional trouble shooting could isolate/verify the cause and/or even fix it, inexpensively. Some examples........

Your profile does not show your location or model year. In the U.S., from MY 2001, an emergency truck release switch was added to the inside of the trunk lid. It may be stuck in the truck open position or as reported by other owners, the wiring insulation has chafed on sharp edges inside the trunk and shorted out. BTW, all of methods to open the trunk, including the mechanical key, will turn on the center console switch lamp, until the truck is closed.

The trunk locking mechanism (e.g. S15/1), operates by pneumatic pressure, supplied by the Pneumatic System Equipment control module (A37). In addition to being central locking system air pump, other combined functionality pertains to the power roof controller and alarm systems. Air pressure is supplied to the locking mechanism via a plastic T valve and 2 pneumatic lines, which then actuate a lever, that locks / unlocks the trunk. Unfortunately, with age, plastic becomes brittle, so I would check for broken connections, leaks, movement the actuating lever etc. See pictures in second enclosed thumbnail.