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Hello my 500SL is a new purchase came with the hard top in place PO told me they replaced the soft top and it is new,, Seems though that the top only goes to the 12 oclock position then the light flashes and motor stops working with the top held in that position. 1993MY .
 

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Did the installer mistreat the bow extension cylinder micro switch?

Benzalan,

Thank you for the detailed description. That leads right to the most likely cause for the problem: the left bow extension cylinder micro switch.

There is a micro switch on the left bow extension cylinder, see the diagram below with the location of all cylinders in your car. The left bow extension cylinder is located inside the soft top frame, up about a foot from the main lift cylinder. The switch that is mounted to it communicates with the soft top controller. If you follow the wiring for that switch, you will find that it connects to the wiring harness behind the driver's door, a few inches below the door striker. It is a bit of a pain to get to that point, but you will probably have to do that.

If that micro switch does not change position when the top approaches the 12 o'clock position during the opening cycle, then it will cause the top to stop the cycle just as you have described.

Likely, the installers of the new soft top have either not reconnected the micro switch to the wiring harness, or they have accidentally crushed it when swapping cylinders for some reason.

Three ways to test it:
1) Visual inspection. With the ignition off, manually push the soft top forward to rest on the windshield header. Hold up the rear bow (window) while you are doing that. With the rear bow up, look for the switch on the left bow extension cylinder. If it looks crushed as in the photo below, or bent in any other way, then you know you will have to take it off and replace or fix it. See the following thread about fixing the switch: http://www.benzworld.org/forums/r129-sl-class/1547193-1996-bow-extension-micro-switch-fix.html#post4363007

2) Audio inspection - try to hear if the switch clicks. With the top resting on the windshield and the rear of the bow up, move the rear of the bow forward and back while trying to hear it click when the bow is near the upright position.

3) Electrical test. Locate the connection to the wiring harness. You may use part of our removal instructions to get there: http://tophydraulicsinc.com/R129 Bow Extension Cylinder Removal.pdf.
Connect a multimeter to the wires leading to the switch, if you want to, and see whether it changes resistance when you move the rear of the bow near the upright position.
The ultimate test is the following: short the connector to the wiring harness with a wire. That simulates the switch giving a "closed" signal. At that point, you should be able to close the top all the way with the hydraulic system. (You won't be able to open it without removing the shunt, though...)

If the switch should be bent, you can carefully remove it with a Phillips screwdriver and replace it without removing the cylinder.

Please let us know what you find.

Hope this helps,

-Klaus

[email protected]
 

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