Damppe

Hello!

Cabriolet roof wont open. First i open the roof and pull it up a little bit, when pressing the button windows go down and nothing happens after that. The button is RED. Can it be something with the rear headrests , they are up and donīt move when pressing the button up&down, i only hear a relay clicking noise and the button light is red.

Anyone here with similar problem?

Comment what you think or know it to be.

Thanks!

marko69

Headrest not working, top not working but you hear the relay clicking. Pump is not operating. Check fuse #13 in the trunk.

Damppe

Fuse #13 checked, 40A and was OK. What now?

marko69

Bummer.
You'll have to gain access to the pump by taking off the big metal plate in the back of the trunk. Do a search on gaining access to the hydraulic pump. It's not hard, just a bit time consuming.
You hear the relay clicking so all the limit switches and controls are good. Either power is not getting to the pump or the pump is bad. It's just a simple circuit to get power from fuse 13 to the pump. 1 fuse, 1 relay, and a few connectors and wires.
First try swapping the hydraulic pump relay with the fuel pump relay, they are the same. IIRC the fuel pump relay is rear of the fuse box in the trunk and the pump relay is to the right of the hydraulic pump. Also double check fuse 13 to make sure the legs aren't corroded or pitted.

Serndipity

At this time, it could be any number of things.

Have you checked the level of your hydraulic fluid?

If it's low, the power roof/roll-bar system may have insufficient hydraulic pressure to operate, which likely is caused due to a leak (e.g one of the 8 hydraulic cylinders, a line etc.).

If OK, malfunction is more likely to be electrical (e.g. voltage supply must be between 11 and 14 volts, pump motor relay, faulty limit/position switches, proper locking sequence not confirmed by the controller, wiring etc.).

Consider having a qualified tech run the MB STAR diagnostic system and get a print out of any trouble codes related to the power roof system / roll-bar system.

marko69

Correct me if I'm wrong here Serndipity, but you wouldn't hear the relay clicking if any of the N52 control inputs were incorrect like the limit switches. When N52 sees all the controls good, only then it sends power to the pump relay to operate the pump. Even with a low fluid level the pump should run unless there is a switch at the reservoir that's not on the schematic. (I'm assuming the OP doesn't hear the pump running, maybe I shouldn't have assumed that)

Serndipity

Hi marko69,

I remember you......about a year back you diagnosed a difficult circuit 30 voltage supply problem, where although the fuse looked fine, it's contacts within the relay box where corroded.

The N52 controller evaluates the various inputs, from the various limit/position switches and/or CANBus and then activates succeeding outputs, in in a logical sequence that corresponds to each physical stage of power roof or roll-bar operation.

As example, the OP noted that after releasing the front bow locking handle, all the windows lowered, heard a click, but the previously extended RB did not lower, which should have been the next operational step.

Point being, the controller processes the necessary inputs and outputs, one step at a time.

The OP problem description is way to general, to accurately troubleshoot and diagnose, at this time.

As example, the clicking may be due to the controller activating the motor starter relay control coil, that activates the relay armature, but then the relay's contacts that pass the necessary high amperage to the motor may be fried (e.g. over time become pitted and no longer pass the necessary current to run the pump motor). Note: This has been a common problem.

Also note that the 8 hydraulic cylinders are differential by design (e.g. double acting to open/close and/or lower/raise the power roof/roll-bar), which by the nature of how this is accomplished, requires full system pressure to function properly. Note: There is no switch/sensor within the reservoir, so low system pressure (e.g. fluid level) is best determined by visual inspection. The cut away flap, provided in the trunk carpeting, makes this easy to do.

The bad news is that the troubleshooting, diagnosis and repair of old W208 power roofs, is often more than the car is worth.

The good news is that, with good DIY skills and the collective knowledge available, repairs can be done, for pennies on the dollar.

marko69

I agree with you, but I think hearing that the top and roll bar don't work but I hear a clicking (and nothing else), is enough to troubleshoot. The pump is in common with both. Hearing the relay clicking means that you can eliminate all of the controls and switches because the controller likes what it see's and wants to operate the pump as it is sending voltage to the pump relay. If you hear clicking from the relay but the pump isn't operating then the problem has to be the power circuit from fuse 13 to the pump or the pump itself. The OP has checked fuse 13, so the pump relay would be next.
If he didn't hear the relay clicking, then I would suspect the controls and switches.

Damppe

Found the relay and switched with fuel pump relay. Headrests is now moving! Tried opening the Soft top, nothin happened, top Button now started blinkin red when pushing the Button.
After that i opened the trunk, remembered there is a switch on right side that Must be pushed in, closed the trunk, tried again and top started moving, it's now fixed! Must get a New relay.

Case closed

marko69

Glad to see you got it working, and saved a bunch of money!!