I believe the "windscreen" sensor refers to the sensor in the windshield frame that tells the TCM/BCM that you have disengaged the top from the frame. And yes, that is the handle he is referring to.

The sequence (as much as I can remember) goes something like this, assume your top is up or closed:
(I have GOT to get to bed... this may contain errors, but you get the idea)

You are parked and you reach up and turn the handle and disengage the top from the windshield frame.
The sensor in the frame sees this, and it's signal to the BCM causes the BCM to lower both windows.
OBVIOUSLY if you can release the top from the windshield and the windows don't go down, you have a bad sensor up there!!!!


You then hit the button, for anything to happen further ALL of the following has to be true:
1) You are going less than 9mph.
2) The divider in the trunk is deployed. (And that sensor has indicated such.)
3) The trunk lid is COMPLETELY closed. (And that sensor has indicated such.)

At this point, hitting the button causes (and you can hear this if it is quiet around you) an electric lock to activate in the trunk, this locks the trunk so no idiot can open the trunk in the 23 seconds it takes to raise or lower the top. The electric cam moves in about 2 seconds. When the sensor in this mechanism tells the BCM/TCM that the trunk is now locked, the hydraulics start to activate. There will be no hydraulic motor operation until this point!

The pump starts, the latch holding the window to the lid is released and valves move such that the cylinders are activated to lift the window. Once sensors indicate the window is up all the way, the hydralics release the deck latch and the cylinders are operated to open the lid.

When the lid is open all the way, sensors on the cylinders tell the TCM - it commands the pump to stop, and valves are then activated so that, as the pump restarts, the top itself moves into place (that is, moves into the storage area).

Next, sensors on THOSE cylinders tell the TCM that they are moved all the way. Now, the pump is stopped and more valves activate - the pump is restarted, and the lid cylinders are moved to close the lid.
The latch is activated hydraulically to lock the lid closed.

The electric lock is reversed to the unlocked position in the trunklid.
The system beeps and you are done.

The reverse happens when you put the top back up, of course.
So you see how many, many sensors there are. I have not experimented to see if the top will stop moving mid-stream like it does with you if any of these sensors fail, but I am SURE the one for the divider WILL cause the system to freeze (this is why we suspect it).

As to the one in the windshield, I don't know. Same for the one in the electric trunk lock.

Also, I am unsure of just all the interactions between the BCM and TCM, I DO know they work together to make all of this happen.


I do not believe they are electronic sensors, it is my position that they are mechanical switches. I also believe they are closed in their "ok to move" position, but am unsure. I DO know the sensors on the electric lock are plural. That is, there is one sensor to tell the system it is fully unlocked and one to tell that it is fully locked.

There is a good description of the sequence in the service manual. It includes a schematic of the hydraulic lines, pump, cylinders and valves. You can ONLY fix this yourself if you have a basic knowledge of how it operates so that you know what might be missing from the puzzle!

The service manual is hard to read (like so many auto manuals) but as you read and inspect the car, you will "get it".


I still say it's the divider switch, windshield switch or electric cam lock switch(es). Either that, or you are trying to move the top while moving too fast - but you've had the car too long for that to be it.