On Sunday I had a spontaneous failure of the sliding roof. It was a bit open and could not be closed again, just open further. So on the way I looked at the safety plan and found that only the fuses and not the relays are marked on the safety plan. So that there was nothing really to be done on the way. At home in the garage I then dealt with the function of the roof and for every function of the sliding roof in the schematic of the rear control unit A relay found. Only in the relay layout of the rear control unit these two relays do not appear. Probably because they are mounted on the body. The self-help on the way (e.g. in the case of rain) would therefore have been no problem at all, if one had known the location of the two relays. Because water in the control lever module is suboptimal. After exchange of the two relays it was established that the locking relay is defective. The measurement later revealed a too high resistance of the coil. ch incomprehensible why on the inside of the fuse box cover the complete occupancy, as on the W163, is not printed. I took a photo of my rear control unit and labeled it. Depending on the equipment, the occupancy can vary. There are only 4 different relays installed in the whole vehicle and some of them also as reserve assembly. That means you can change in case of an emergency besides the reserve relay also a relay from an unneeded function. Sliding roof errors can be used with the relay from the rear wiper engine or with AdBlue errors the relay from the rear windscreen heater. For the fuel pump 2 reserve relays are inserted in the rear control unit and 2 relays in the front of the front of the passenger. The relay from the rear disc heater can be converted from the rear control unit into the front of the front of the passenger as starter relay.