When I raised the glass on the passenger side to close the window on the Vito (W639) it powered fully up and then made a high pitched ‘Boing’ noise. After which, although the motor was heard running, the glass did not move in either direction.
It is quite common for the rise and fall mechanism in the door to give problems once the vehicle is a few years old. What normally happens is the plastic slides that move the glass up and down on two rails weaken, causing the bowden cable to break away from the captive part of the moulding. Once one end of the cable becomes detached the window will no longer work correctly.
There are some great quality cheap service kits available (Ebay) and before I ventured to get started on the job I ordered a repair kit. The kit consists of the steel cables with three sleeves, two plastic slides and a new fitted gearbox and spool mechanism. (Other more comprehensive kits including full slide rails can be obtained, dependant on what you need and wish to pay) Mercedes dealerships will normally charge you £160 parts, plus 3 hours labour per side so the £10 kit represents good value for a DIY job.
The DIY job is fairly straight forward and depending on what part is broken the job could take anywhere from an hour and a half to three hours to complete.
The first thing to to do is strip the door down, removing the trim panel (door card) to gain access to the mechanical parts needing replacement. Before you start, spray some WD40 across the top of the trim panel where it joins the rubber window seal, this is important to aid removal, as often the plastic panel ‘sticks’ in the rubber channel making it difficult to lift off.
Now prize off the top trim cover from the handle, there is a small ‘letterbox’ hole at the base to assist its removal by inserting a screwdriver and releasing the plastic latch. Once this part is removed, undo the two torx head screws securing the handle to the door. Beneath the door pocket are three black plastic expanding fittings, these will unscrew and allow the retained expanding piece to be withdrawn, releasing the bottom of the panel.
The door panel is now only held with a number of green plastic mushroom trim clips on all remaining edges, insert a broad screwdriver between the trim panel and door and release them one by one. When all the clips are released, tilt out the bottom of the door about 4-5 inches and lift carefully up. This should release it from the rubber window seal, if not do not use force at this point, as if the panel releases quickly, you will be fortunate to stop it ripping off the wires to the tweeter speaker and possibly the electric window switch. As you raise the panel up and off the door, reach behind and disconnect the door tweeter/speaker connector from on top of the bass speaker and then the electric window switch assembly cable. Unclip the door handle steel cable from its retainer block and place the panel to one side.
You will be faced with the inner membrane covering the door apertures and before you can fully remove this to gain access, you will have to remove the main bass speaker (4 screws) and the door control module. The door control module is the square unit where all the wires connect to, push in the two latch clips and release the leading edge, lever slightly out and slide forward to release the rear locating tabs. Pull out all the wiring connectors and fully remove the module.
Using a sharp blade or craft knife, cut through the mastic that holds the door membrane to the door, this will take some time to do without damaging the membrane material. It may be easier to ‘peel and cut’ the mastic as you go, all around the edges of the cover, after a while you will have free edges. Lift off the membrane and store it. If you were careful to cut it without damage, leaving some mastic on both the door and membrane panel. It will ‘re-stick’ when it is time to put it all back together, without the use of any other glue or tape. For this reason it is worth taking the time to do it carefully so as not to cut the material itself and leave mastic on both of the mating surfaces.
Now the membrane is removed access to the interior is possible. Temporarily re-fit the door control module and reconnect the cables, operate the window from the other door or re-fit the control switch. It is now you will get an idea of what the issue or problem is with the window lifter. I felt inside the vertical rails and both bowden cables were present, running in their respective guides and taught. Realising that the slide assembly was fully intact it could only be one other thing the motor spool gearbox. A new spool gearbox was supplied in the kit and I felt it unnecessary to replace all the parts as I could gain access to the faulty gearbox without removing the full rail assembly. (Saving unnecessary parts being replaced and of course time)
On removing the three self tapping screws from the spool gearbox the moulded cover lifts off, revealing the spool and cable entry/exit portion, now separated from the window lifter motor drive shaft. Instantly I could see the problem – the main gear drive that locates into the lifter motor had sheared cleanly from the spool moulding. All I was going to do was replace this part taken from the service kit.
The spool can be pulled from the housing and the cable outers released from their slotted retainers. As you do this it is a good idea to note how the cables are routed and especially how they are wound and positioned round the drum to aid reassembly. Unhook the cable from the bottom of front lower guide rail, this will give you the slack you will need to wind the spool correctly.
Having fished out the broken gear from the motor unit, the gearbox can be refitted. All that remains to be done is to feed the bowden cable inner around the lower guide rail, pulling the outer (quite hard) to be able to re-seat it in its retaining slot that makes up part of the corner guide. Test the window, if all is well start to rebuild the door.
Obviously the problem with your window mechanism may be different than that found here and it may require the full removal of the mechanism (A little more complex and time consuming). Details of the full procedure are well documented here in a very good video by Scott Elliott, to which I cannot add much to his excellent description of the work to be done.
Remove the door control module to begin the rebuild, refit the membrane threading the electrical connectors through the appropriate cut-outs, push the mastic edges together to seal the membrane to the door. Finally locate the door control module and plug in all the connecting leads and cables. Each cable has a unique plug/socket arrangement so it is impossible to connect this wrongly. Once you are satisfied with your work, offer up the door panel. Reconnect the door latch operating cable, the window switch and tweeter cables, then locate the top of the trim panel into the slotted lip of rubber window seal, feeding through the door lock pin as you go.
Once this is in position you may finally position the panel to the door, ensuring where possible the trim clips are aligned with their respective holes. Use the palm of your hand to pat the panel onto the door, this will seat the trim clips around its perimeter. Now replace the three black expanding clips under the door pocket and finally add the two torx screws that fasten the door handle to the door. Clip back on the handle trim and the job is done.