996 Convertible Not Completing open or close

2003 996 Cabriolet � Violent Shaking Mid-Cycle / Not Reaching End Positions / Microswitch Question Hi all, I'm hoping for some guidance on a 2003 911 Cabriolet (996), ~104K miles. Issue: Convertible top doesn't complete open or close cycle. Convertible top operates, but at about 2/3 through the opening cycle it shakes violently Closing is normal No clicking/ratcheting just strong shaking/bouncing Additional Symptoms: Right side of clamshell sits slightly high when closed (left side is flush). I adjusted the rubber clamshell stops but had no effect. If I press it down on clamshell it springs back up Dash shows top NOT fully closed → windows don�t roll up. Same when opening → not recognized as fully open System never reaches a true �complete� state Latch / Mechanism Observations: Front latch latches and clicks normally Rear latch does not have a noticeable strong click, there is a faint click. I was able to access the rear latch mechanism: With the top almost fully open, I can manually move the mechanism and close the latch In partially/fully closed positions, it will not move manually (seems position-dependent) Microswitch: Located a 2-wire microswitch with a red plunger near the gearbox It does not appear to be fully actuated during normal operation What I�ve Done: Inspected linkage � nothing obviously loose Lubricated moving parts Checked and adjusted clamshell stops Observed actuator movement (appears limited) Reviewed Porsche service manual � calibration requires all microswitches to be functioning Question: Does this point more to: Rear latch not fully completing travel / not triggering microswitch? Slight misalignment (right side sitting high preventing switch activation)? Drive cable / gearbox not achieving full travel? Microswitch itself faulty? Notes: Assisting the top by hand does NOT reduce shaking System never reaches a confirmed �open� or �closed� state [size=13px] Likely Cause (my working theory): Top is not reaching final travel to actuate the rear compartment microswitch, so the control unit never sees a valid end position and the mechanism oscillates under load. -- Any insight appreciated � especially from anyone who�s dealt with rear latch/microswitch issues on a 996 cab.[/size] Thanks in advance.

From your description, it seems the right & left sides are not aligned with each other. i.e. one side seems higher than the other. Meaning one hydraulic cylinder is ahead in relation to the other hydraulic cylinder. First, remove the rear speakers, pull the black piece of plastic isolating the cylinders from the speakers wiring and do a visual of your hydraulic cylinders, the seals may be Kaput on one side causing an unbalance. If not good, remove rear seats, side panels, access the cylinders and remove them. Be careful on driver side to not disturb or damage the potentiometer attached to a plastic rod mounted onto the side of the cylinder, have those cylinders resealed properly by a professional. (I can recommend one for a decent price). If all good, what i would do then, is put the top in service mode position, access the hydraulic pump by pulling the back window storage cover out, then unplug both banjo screws securing all 4 hydraulic lines, put a BIG towel under the lines to catch the oil, and manually move the top by hand up and down several times. you may experience resistance at the beginning due to oil still in the cylinders, but after a few up/down, your cylinders should realign themselves (provided nothing is bent) and you could try to latch the top in the close position. Make sure you hold the top when you unlatch it so, it does not go down crashing in the rear window storage location. (ask me how I know). If all is well, I recommend you remove your pump from its bracket, flush the old oil and gunk as much as possible, put new OEM oil way past its upper MAX mark and reinstall. Use new brass crusher washers (in the right order) and banjo screws. The mechanism is self-purging, so with new oil in the system, carefully & slowly activate the up & down several times to flush air bubbles off the lines, top the oil reservoir with more oil to the MAX (one can of 250ml OEM 000-043-305-50 will suffice), clean up the mess and move on to the next problem. Good luck!

Thanks. I replaced both hydraulics about a year ago with rebuilts and the top has operated properly . I inspected and there are no apparent leaks and fluid level is at MAX . Do you recommend I bleed the system and refill ? Since the top closes and latches properly, I suspect the issue is the gear mechanism that pulls the cable that closes the clamshell latch or the microswitch that signals that the latch is closed . Let me know your thoughts .

Convertible top operates, but at about 2/3 through the opening cycle it shakes violently Closing is normal No clicking/ratcheting just strong shaking/bouncing Additional Symptoms: Right side of clamshell sits slightly high when closed (left side is flush ). I adjusted the rubber clamshell stops but had no effect. If I press it down on clamshell it springs back up That is where I have a problem. I personally think your hydraulic cylinders are misaligned in relation with each other. And the fact the opening cycle has issue midway seems to enforce the misalignment. Next, your clamshell does not sit straight, again the right cylinder seems to be slightly higher than the left and do not complete its course to allow the clamshell to rest properly down. The left side is the reference since it has the potentiometer. Before you start messing with the hydraulic, can you measure the distances of the cylinders moving part edges in relation to the cylinders own anchoring points and compare the right & left cylinders exact positions. At open top position, with top parked under the clamshell, both moving parts of the cylinders should be sitting at the same distance from forward nut. something like 5/8" maybe. You probably have a discrepancy of 1/4" or so between left and right references. Since you need to access the hydraulic pump, you'll need to adjust while top is up. Since you got both side covers removed already, activate the top up command closing the top to the point where the left side of the top is aligned properly with the windshield frame and close to ready to lock. The right side should be off closer to the frame a bit. At that point, release the pressure of the hydraulic lines that force the oil through the cylinders (by unscrewing the banjo screw slightly at the pump. I do believe you need to unscrew the Red line that feed the up motion to release the pressure and allow for the right cylinder to move backward down a bit). then, manually push back the sliding part of the cylinder till the top right mechanism aligns with the windshield frame properly - same gap- AND level with the left side of the top, up to the point where the ECU knows it can latch on (i.e. microswitch activated). Due to pressure within the cylinder, you may have to clamp the moving part or ratchet in to move it. 1/4" or so toward the front nut will push the right side top backward. Meaning that when all is aligned, the top will slide further down when clamshell is closed. Clamshell should then close straight. When all aligned and dandy, tighten the hydraulic line back, and test it 3 or times up & down. Good luck!

I am looking for Rear Drive Unit Part# 99756102101 . Is there anyone that does rebuilds? What I am finding on line is $3K-4K for new OEM and used are scarce and about the same price. 99756102101 replaced 99756102100 and 99656102104 so they should work as well.