The convertible top is self leveling. There is only one motor that supplies pressure to two cylinders that raise and close top and another that raises and closes the cover. The control to keep this in check is called the Convertible Module, CVM, and there is another module called the General Module.
There are four Hall Sensors which measure the angle of the cross member, referred to as a, "Bow" and another to measure the angle of the linkages relative to the "B" pillar. Then there are two more, one for each locking mechanism of the front windhield mounted lockdowns.
So the are 2 pistons that raise/lower the top and the angle is sensed by the hall angelsensors which in turn control the 2 hydrulic pistons to keep the top level and to know what position it is in. There are 2 solenoids to blow off extra pressure after the top is raised or lowered.
So, there is only one hydraulic motor for the whole sytem and 2 piston assemblies, much like shocks with pressure on each side of the internal piston, which are the power source that raises and lowers top and the hall sensors which keep it all at the proper angle.
There is not anything to synchronize as it is all elctronically controlled. If you are having issues with the top lifting at an angle that is not flat as it should be, there are a few things that could be wrong;
The most likely scenario is a failed hydraulic piston or hall bow angle sensor as these are what keeps the top level. The motor would either work or not and the top would not move. All of this is controlled by the CVM and there is a possibility that it has failed.
My best advice is to get the trouble codes pulled yourself and see what comes up. There does not need to be a warning light on in the instrument cluster to have a code present. Any
Advance Auto or Auto Zone will pull the codes for free. They will give you a short description of any electronic failures. If you do not get a code, the the CVM is probably okay and the problem is in the hydraulic piston lift assemblies and the one that is lagging behind might have a bad seal or a clog in the line that is keeping it from working.
The fluid level for the pump could be low. It is located at the center under the rear seat. Because BMW has not released the information in regards to the type of hydraulic fluid because it is propietary. You would have to go to a dealer to make sure you get the correct fluid as there is no, "Standardized Fluid" that you can purchase at a parts store.
So, get the codes pulled first and if nothing comes up get a repair shop to check the pistons and the lines and fluid level.
Again, I did not find anything in regards to synchonization as there is only one motor.
Wednesday, December 21st, 2011 AT 12:42 PM