1988 cabriolet top closing problems

[megerian]

Well, I probably jinxed myself...

I was out cruising on a beautiful Sunday morning here in Minnesota, and I was thinking how nice it is that everything on the car is working so well, and running so smoothly.

So I get home, and as I have done countless times before, I push the button to close the cabriolet top. As the front bar of the cab top gently hits the top of the windshield, and its supposed to engage the closing motors... nothing. Everything just stops.

It will not close, and if I push the button to open it back up and restart the process, nothing happens.. crap!! So now the cab top is resting on the windshield, but not closed.

Since I have read and contributed to many threads about alignment, I know its not that, since both sides are aligned together. I can also see that the two little microswitches are tripped, which SHOULD be telling the brain that it should engage the closing motors.

When I push the button rearward to try to open the top, I hear a faint click. When I push the button forward to close the top, I hear nothing.

Is it some electrical situation where the brain got confused? It has been working perfectly for 2+ years. Could it be a fuse or relay?

[porsche964guy]

1988 cabriolet top closing problems

Hi, Had same issue with my '90 964 CAB, sounds the same. First make sure the two micro switches are working using a multi meter. Don't just listen for clicks. If they are then test each motor to make sure the work. You can put power to them from 9volt battery or from cigarette lighter . Be careful to use right motor input contact wires of the four. If they don't work they could be frozen up because the notorious brass gear is shot. By the way now you can buy just the brass gear and worm gear drive set repair kit offered by URO parts now (the complete motors are about $1000 if you can find them). If all this is OK then it is your top controller under the dash above you left leg. A hard part to get at.
Good luck.
dj

[megerian]

But why would that prevent the top from opening back up? If I put a little upward pressure on the front of the top, to disengage the switches, then pushing rearward on the opening button should cause it to open, but nothing happens.

[porsche964guy]

Its a fairly complex system having micro switches in the rear at the lift motor gear right side, the two in the front of the top and one in each lock motor. All sending status current to the controller. I would check them out first before going after the controller. You can loosed up the bolts at the two base hinges and open and close the top manual if you have too. I put temporary switches for each lock motor until I have time to get at the controller.

[megerian]

One other symptom, when I push the "open button" the dash lights dim slightly, and there is a slight click, but nothing happens.

Also, can anyone answer this question: My wiring diagram lists fuse #3 in the luggage compartment, but it also lists a "power top fuse" and a "power top fuse holder". Where are those located?

[megerian]

Fixed it - after checking the #3 fuse, and the dedicated cabrio top fuse and finding both to be good, I opened the right rear side panel. By unscrewing the white switch and allowing it to release, everything started working again.

I *thought* that the switch just acted as a mechanism to tell the control unit that the top was all the way forward. In reality, the white microswitch seems to act as a fail-safe to stop all operation of the top, probably to prevent any damage.

What I now believe happened: while I normally guide the top with my hand, the most recent time it must have closed a bit more abruptly than usual, and it tripped the white switch, and turned everything off. I thought that even with the switch engaged, you should be able to push the rocker backward and open the top, but that is not the case.

[kidrock]

what is this "white switch" you speak of, and where exactly is it located?

[megerian]

When you remove the right side panel, on the side, right next to the rear seat, that hides the right side control arm. The right side cabrio arm assembly on the right side has two white switches. This is same panel that is holding the right rear stereo speaker.

One white switch gets depressed when the top is completely open, and stops the motors from running, and turns off the red light on the dash. The other one ( I thought ) gets depressed when the top is completely closed, but I was wrong, it should not be depressed during normal operation, since it appears to act as fail-safe.

I think I have a photo here somewhere...

[megerian]

Here is the photo, the one with the white switches is the right hand side assembly

[boyt911sc]

I've been following this thread since I have almost identical problem like yours. Could you elaborate on your troubleshooting procedure? Accompanying pictures would be great. PM sent. Thanks.

Tony

[mysocal911]

Originally Posted by megerian

Fixed it - after checking the #3 fuse, and the dedicated cabrio top fuse and finding both to be good, I opened the right rear side panel. By unscrewing the white switch and allowing it to release, everything started working again.

I *thought* that the switch just acted as a mechanism to tell the control unit that the top was all the way forward. In reality, the white microswitch seems to act as a fail-safe to stop all operation of the top, probably to prevent any damage.

What I now believe happened: while I normally guide the top with my hand, the most recent time it must have closed a bit more abruptly than usual, and it tripped the white switch, and turned everything off. I thought that even with the switch engaged, you should be able to push the rocker backward and open the top, but that is not the case.

Both switches that 'follow' the right top arm are limit switches. They prevent the
cable drive motor from damaging the top frame arms. The up limit switch must
not close before the two top switches (sense the windshield frame) close or the
locking motors will not function.

[megerian]

Dave is correct.

So what happened to me was that the top closed a bit more quickly than normal, and the top limit switch was closed before the locking motors could engage.

Of course, I didn't know this, so I first verified that the fuses were all intact and that the emergency brake sensor was also working. Then I took off the right rear speaker panel. This comes off by removing a single phillips screw and a plastic rear push screw. The panel lifts off, and you can then remove two speaker wires to detach the panel completely and set it aside.

Then you will see the cabrio assembly as seen in the photo above. The right side assembly contains the two white switches. In my case, the top white switch had been depressed by the control arm. While that seemed normal to me, since I thought that the top limit switch just told the control unit to stop closing the top, I figured I would unscrew it to release the switch and see what happens.

Voila - once the white switch was wiggled out of the way enough to release it, the top went back to working. I then tightened it back up, and opened and closed the top several times, and saw that in normal operation, the closing motors activate before the white switch is closed.

So I believe that the key is to guide the top with your hand and not let it "slam" forward even a little bit, because that can trigger the limit switch.

Once I tested it a few times, I reattached the speaker panel and all is well again.

[kidrock]

cool, thanks for the detailed explanation by all. Glad to hear you got it working again.

[89cab]

I just Emailed you I have a great PDF with some great info about Carrera tops..

[megerian]

89cab - thanks, I just emailed you and would love to get that PDF.