mikefo

I am new to Porsche although I have had and maintained many BMW's. I recently purchased a Black/Cashmere 95 cab with 13k miles on it and drove it back home over 1,300 miles with no problems. Over the last few weeks I have been sorting out the car fixing the squeaky windshield (White lithium grease applied to bottom seal), changing front/rear hood struts, new caps and arms, cleaning ISV valve, changing plugs as well as the right side lower valve cover.

Success in all fronts other than a cab top problem that started this week. Top has worked fine with the exception of a twanging sound (think banjo string being plucked) I suspected was the top cables. This did not effect operation. Over the last few day I have been upgrading the Stereo from the Hi-fi package to something that sounds good while leaving the stock look. This included replacing the rear speakers as well as the AMP under the passenger seat. After the Stereo upgrade, I lowered the top halfway to clean / lubricate the top/bottom seals (again with white lithium). Then re-closed the top. When I re-closed the top, the top-down dash warning light would not shut off.

At this point I tried to re-open the top. The latching mechanisms work in spits when opening perhaps releasing 1/4 of the way and then stopping. Pushing the button again causes it to release another 1/4 way. Eventually the latches fully release the top but the motor that drives the top refuses to turn on or make any noise at all. I can re-secure the top as the latching mechanism works perfectly when securing the top with the top-down dash warning light does not turn off although it has once after I returned to the car after not driving for a wile and pushed the top down button. The light had been extinguished although it has since returned after trying to open the top and I have been unable to extinguished it since. Reading the forum I became convinced the convertible top control unit solder joints were the problem https://rennlist.com/forums/993-foru...em-solved.html and pulled the control unit (easy if you pull the ventilation duct as it provides easy access with the use of a mirror). Had the complete unit re-soldered with no change in result although perhaps it will be preventive maintenance.

I pulled the passenger rear seat panel and examined the 2 sensors. They seem operational and in contact with the control arms. Looking at the top, I located 2 sensors that also appear to be operational (they still move freely).

Any suggestions or help would be appreciated as the next step would be to take it to the dealer (something I dread out of principal) or make it a manual top (something I hate to do as the car is a 9.5 out of 10 car and I intend to keep it in this condition).

Thanks in advance!

porschemikeandnancy

My own '05 cab had problems when I purchased it. Top would not either open nor close every time. My independent shop (who is very familiar with the cab. power top) told me the cables and some control module (in the rear of the car) is very sensitive to being properly aligned. They did an ajustment plus replaced one "module" for a couple hundred bucks. Has worked perfectly since.

One thing I was also told is not to open or close the power top when the car is on any angled surface. In other words, try to operate the top when the car is almost level.

CalvinC4S

There are a series of micro switches in the top mechanism that actuate the functions your top go through in a full cycle. Two of the adjustable micro switches are in the panel just left of the drivers side back seat( might be other side, been awhile). The micro switches that actuate the top locking to the windshield frame are adjusted by the two guide pins by screwing them out or in.

If you put speakers in the carpeted covers that go over your top transmissions, you might of knocked the micro mounts out of position.

9 out of 10 times these switch adjustments are the issue, excluding L/R timming issues which isn't the problem.

Sean Hamilton

It’s a closed circuit – only one micro switch needs to out, or a plug not connected properly or a blown fuse and the whole system will go haywire. You may have knocked one of the two transmission micro switches when installing the rear R/H speaker. When looking at the transmission the lower micro must not be in contact until full lowered – it is a limit sensor that tells the central informer to stop the rear motors. The upper must not be in contact until full closed – it’s also a limit sensor and signals the informer to stop the rear motors when the cab top is closed or when the windscreen latch micros come in to contact signalling the latch motors to kick in and take over and latch down the top. Also recheck the 4 pin connector for these micro’s – it needs to all the way home else the cab top will not function.

There are actually 4 micro switches for the windscreen latching process: one either side of the latch motors which you can see are visible and adjustable by two Philips head screws. These trigger the latch motors to open or release the latches when they come in to contact. They can be adjusted closer in or further away – too far out and the latch motors wont engage, too far in and the latch motors start too early.
My experience is that if the cab top warning light won’t extinguish then it is truly not closed all the way. It only needs to be a millimetre out and the light will remain on. And the micro switches only need to be out by the same and the top will not function as it should. I’ve found it can also just need a jiggle to get one micro in sync to the other is all it needed.

The other two micros are inside the latch motors themselves and are critical in signalling the informer the rotational limits of the latch mechanism in closing and opening. These micros are activated by a cam gear inside each motor that rotates the latch. This is where I was having trouble with one cam micro not in sync with the rotational limit and telling the central informer that it was at its limit yet the latch had not fully rotated and the top and warning light was not fully closed. There’s a grub screw on the face of the cam to adjust its proper contact position with the micro.

Sean.

95 NC 993

Was just wondering if the prior owner had the 'recall' done for these? I have no idea what mechanicals were involved (other than the locking mechanism) but my '95 cab was done by a dealer before I bought it. I do not know if you can still get the work done under the recall. Maybe someone has personal knowledge.

mikefo

Thanks for the ideas. Yes, the previous owner had the latches replaced by recall along with the engine wiring harness. I checked the fuse (twice) and it seems fine. I tried adjusting the micro switches on the rear passenger side but they seemed fine. I adjusted the #1 switch to be tighter and the latches quit working so I adjusted it back to previous position (Basically midpoint). In any case they both seemed to be secured tightly. The wiring relay plug was a prime suspect as it was likely stressed by the speaker placement. A close inspection reviewed no problems though. It is possible one of the relays was damaged by pulling the wires during speaker installation although the damage is not evident.

At this point, I suspect the top (Windshield) micro sensors. Are they easy to access? Sounds like a Sunday afternoon project.

Chuck W.

I had a simular problem with my cab and re-soldered the board. The problem continued so I bought a used unit and that fixed the problem. See if you have a Rennlist brother with a cab close by and swap units. Good luck.

RDS928S

My top was replaced by the previous owner & the twanging noise is un-bearable everytime i hit a bump. No idea what to do next?

Regards Rich

mikefo

I am sure that it is the micro switches located in the top near the windshield. The top actually worked a couple of times after messing with the micro switches. Any idea how to get at the switches? Do i need to pull the top frame off or simply pull the two screws near the top that you can access with the top up?

CalvinC4S

those front sensors only tell the top when to stop latching. Look closer at the front micro switch in the transmission. This is the switch that tells the control unit "ok we are all the way forward and ready to latch her up". If I was in Vegas I would put my money on the forward micro switch of the two in the back.

Andre'

Had similar issues with my '96 - the Porsche dealership couldn't really find anything wrong and brought in some "Porsche Engineer" from Porsche North America; whatever that means. Her advice was since I used to stop the opening sequence half way to put a towel on the rear window before it folds up (to prevent scratches) to open the top in a single pass. Same with the closing sequence. I also found and can confirm that opening/closing the top on a level surface causes less issues but I'm still having problems every now and then. Last time the top warning light came on because of only the right locking motor working, and then 4 days later the whole issue disappeared basically over night...

Don't really know what's going on with the top; welcome to the club!!

Andre'

Sean Hamilton

My understanding is the front windscreen micro's tell the latches to begin rotating when they come into contact with the windscreen. This can be tested by moving these micros backwards away from the windscreen - try it, the cab top will come down and rest against the windscreen and the latch motors will not start up because the micros haven’t come into contact or are out of sync. It seems to me it is actually the hidden cam activated micro switch inside each motor gear assembly that tells the latches to stop rotating for both closing and opening - they are the "latch" limit sensors. I’ve split my motor cases and adjusted these cams with success. However, it is crucial the front windscreen micro's are in sync and in just the right position, and it can take a bit of patience to fluke the right position. For the front micro's, just remove the front trim piece – two trim screws and pop it off. You'll see the motors in there and the adjustable micro switches accompanying each motor. https://rennlist.com/forums/993-foru...r-replace.html
But it beats me why these should be the problem when you weren’t working anywhere near this area. I'm with Calvin on this - I'd still be looking down at the transmission micro's - depress either in while the cab top is say mid way or so through closing or opening ..... they appear to simply signal the rear motors to cease operating, being the rear motors limit sensors. Wondering why yours were set at midway – being limit sensors I would’ve thought they should be almost at the very limit of their elongated slot adjustment, as mine are.
Good hunting !!

mikefo

Problem solved! Cleaned microswitches in the top near the windshield with electronic cleaner and adjusted positioning. Works perfect now. Hopefully the solder job on the control box will prevent future problem.

mikefo

Problem solved! Cleaned microswitches in the top near the windshield with electronic cleaner and adjusted positioning. Works perfect now. Hopefully the solder job on the control box will prevent future problem.

Chuck W.

Good deal! Nice job.