aircooledX2

I have searched a bit but have failed to locate a step-by-step guide to convert my 964 CAB top to a partially-manual configuration. At the time of failure my top was down and failed to raise electrically. There are no obvious problems with the components, but I suspect that there may be some micro-switch problems preventing normal operation. At this point I am fine with raising/lowering the top manually, but I'd like to be able operate top latch motors electrically. I possess decent mechanical skills but I lack the detailed system operation information required to design the solution. Besides, I'm sure there are a number of people who have done this with success, and I would much prefer to reap the benefits of their knowledge. Any guidance that can be provided to configure the system to work in a “partial-manual” mode would be much appreciated.

Regards,

aircooledx2

garrett376

It's actually in the user manual! Just disconnect the 19mm bolts at the two rear transmissions which will disengage the rear motors that raise and lower the top mechanism. The latch motors that hook onto the windshield will now be used to pull the top down and lock it once you move the top to the windshield. Once the top is against the windshield, you can hit the button on the dash and the latch motors will pull the top shut. To open it, just hit the button until the latch motors fully release the top then let go of the button. Now you will "manually" open the top by folding it back. That's the semi-manual method.

There really is no fully manual method because there is no manual style latch that I've heard of. The problem with the semi-manual method, is that there is nothing holding the top down when it's in the open position. I would think it would be a requirement to always put the boot cover on the top because the wind could catch the top and raise it up! Normally, it is held down by the rear motors/transmissions - if you disconnect this, make sure you realize nothing is keeping the top down!

SNOWBIRD

I never thought about that before!

Be on level ground!

lvc2

If a top is converted to manual. How hard is it to rehook up for power in the
future? I also read somewhere that there is another small bolt above the top mechanism that needs to be removed as well.
Thanks
Ray



1991 Colbalt Blue Cab
1984 Black Carrera (gone)

garrett376

to convert back - just tighten the two rear 19mm bolts - given all of your transmissions and motors work correctly!

Jeremy Pinsly

Garrett, wouldn't the transmission motors need to be resynchronized if the 19mm bolts are loosened?

Danz C4

If I may say, it's not quite that simple.

Just after I bought my car, I was cycling the top just to see how it worked. It would go up and down, but the switch seemed intermittant and the front latches needed help getting engaged. I have Adrian's book, and have to tinker with things, so I took off the cover panels and found that the PO had epoxied the limit switches to the transmission, and most of the adjusting bolts were loose, with some missing.

So, I ordered a new toggle switch ($30), a new limit switch assembly ($45), and assorted nuts and bolts. I followed the owner's manual instructions to loosen the two 19mm bolts. No problem, top is in manual mode.

New parts arrived, straight forward assembly. No problem. Hummm, motors run, but top doesn't move. I eventually discovered two problems.

1) When you loosen the 19mm bolts, it allows the frame to disengage from the transmission. If you pull the frame a bit away from the hub you will see that there is a mating key and slot that must be aligned before you retighten the bolts. If you don't align the key, you can tighten the bolts, but if you are just a little off, you deform the slot; or, if you are way off, the hub will turn without engaging the frame. Did that, and that...

2) When you loosen the bolts and lower the top by hand, and then run the motor (did that) the ring gear in the transmission runs off the end of the worm gear. The ring gear is not a complete circle, it is something like a 1/2 circle. That means that when you have everything back together, the motors run just fine, but the top goes nowhere. Did that too.

The solution is to detach the lower arms from the frame, attach the arms to the hubs, then align both arms and run the motors to engage the ring gears. You will have to do this with the limit switch assembly not installed because you have to engage the ring gears at a point that the full assembly will never reach. OK, now you can reattach the lower arms to the frame, install the limit switches, adjust the limit switches by the book, and magically, it works!

While you are in there, take timne to adjust the frame side-to-side.

This is actually much easier to do than explain.

Regards, Danz C4

garrett376

Nope - as Danz mentions, the slots will permit you to engage the transmissions in one way only, so you won't get out of sync.

Again as Danz mentions, if you push the switch longer than needed to disengage the top locking/latch motors, you will run the rear motors also which is not a problem. Now if you run them for a long time (20 seconds or so), then yes, you can run them past the gear in the transmission which would necessitate fiddling to get them aligned/synchronized again. But if you do it as I said above, you can do this by simply loosening the 19mm bolts so they stick out about 3mm from their original location to free up the arm from the transmission - you'll know because you can move the top now - that is all there is to it. Just don't press the switch longer than needed to un-latch the top - afterall, nothing is going on so holding the switch doesn't do anything past unlatching the top; and as Danz found out, it makes for more work if you do!

aircooledX2

I have to say that I am encouraged and pleased to see the dialogue that has taken place in the very short time since I posted the query. Thanks to all!

I guess my expectation was that there would be a bit more to this manual business. I kind of thought that there would be some necessity/means to disable the rear motors and leave only the top latches functional - eliminating the concern for freewheeling rear motors, synchronization, etc. Does anyone know of a method of reconfiguring the operation of the system components to inhibit operation of the rear motors and permit operation of the top latches?

I am quite safety concious, and I had some concern for the top not being positively secured in the stowed position. However, I have driven other cars with manual tops that had no reliable means of holding the top down in a sudden deceleration. My concern for this situation is at least partially mitigated by my suspicion that I will have more significant problems to concern myself with if this situation should arise. From what I have read here there may be a need to explore the failure mode that my system experienced if I am to expect to operate the top latches. I'm afraid my understanding of the problem I experienced, resulting in the failure of the top to raise, is extremely limited and I need to troubleshoot some to know what my next step is. Is there a good resource that summarizes the operation of the convertible top electrical system? I would find something like that very useful in my effort understand my present problem and to "reconfigure" the system to operate the way I'd like it to. Manual movement of the top is quite alright with me. I figure I need to get out and install the boot anyway.

Thanks again!

SNOWBIRD

Do you have Adrian Streathers book yet?

Flashtv

I know this was an old post, but really felt compelled to reply. Hopefully you guys see this and maybe it helps another frustrated 964 Cab owner like myself that was almost ready to give up and go to the dealer. In my case, 1990 964 C4 Cab. on a nice drive one day 2 weeks ago, after stopping for lunch, I returned to the car to lower the roof again for the drive home only to discover it developed an issue as I was mid-way through the lowering. It stopped lowering smoothly, began to struggle as it groaned etc. Knowing the sounds and symptoms as well as the horror stories I have read on here of broken bow, arm, cables etc...I stopped right away, tried to raise it back slowly with no success, so i grabbed to tire iron from the front boot and released the two 19m bolts on the tranny's and lowered manually.
Phew, drove home safe and secure, then began the troubleshooting process...

It began as drivers side not moving, to neither one moving. I confirmed that front latches and switches were in good order. Then inspected the inner length of the drive cables connected to the motors behind the rear seat. I had previously shortened some sheathing on the drivers side cable allowing for now 3/4 in. of drive cable to fit inside the motor. That repair was still in good shape, I then looked to the pass. side cable and found it was a bit short so I did the same mod there, cutting 1/4in of sheathing off and then bridging the two pieces with a slightly larger diameter bit of hose to hold it snug then wrapped it in electrical tape, nice and tidy and neat.

After this, still no roof lowering!! Switch was working, motors seemed to be working and making noise, but no tranny arms moving. I could feel small vibration in the cables and the tranny's so I know they were making connections. But no roof movement! Super frustrated, back to more searching and reading. Then I reluctantly decided to follow more suggestions from you guys. I first lifted the roof from the front of the car using the switch and working front latches, then disconnected the roof arms from the transmission arms by loosening the 19m bolts slightly, then disconnecting the first upper connecting arm on each side with the allan head screws. Once I also carefully removed the upper and lower micro-switches on pass. side tranny, I found that I could rotate the tranny arms with very little resistance (first arms still bolted into the key-way slots on the trannys) this did not seem right. Now that that I was able to rotate approx. 180 degrees before hitting a metallic sounding stop, top and bottom, it occurred to me the inner gear was only a 180 half toothed disc driven by the smaller gear motor connected to the cable. Thanks to pictures shared here I could now envision what was in there and I summized that they had each come off the gear? Hmmm could it be?? so one at a time with the ignition powered and a nervous finger on the roof switch i began to work the switch and gently turn the tranny gear towards one of the hard stops and wha-la!! it grabbed the gear, meshed again and began to rotate!!! I then did a little happy dance and then backed it off to its starting point before doing the same on the pass side gear with success again!! (more happy dance) Then carefully backed it off so I could begin them both at the same spot to try and synchronize them. With the switch now, I ran them both up and down a few times to ensure good range, then re-installed the micro-switch pieces on the pass. side again, referencing photos and grease pencil marks. Then with the roof manually down I was able to connect the lower part of the first allan screw arms, then slowly creep the arms into position lining up the holes in the two arms to then reattach the last allan screws.

Finally with a bead of nervous sweat and an imaginary drum roll, I pressed the switch and the roof mechanically rose from the dead!!! Big big smiles but nobody to see it! I ran the roof up and down a few times to observe it landing nicely at top and bottom!! This was a long slow frustrating process for me from both a timing perspective as well as being stumped and failing everytime I thought I had found the problem. This post, that you guys all contributed to was the one that finally saved me so even though this is a long post from me, I wanted to say thank you and hope it helps another person down the road. AND the best part? I eventually found the problem, a solution and fixed it at home and didn't have to pay the dealer. Big win for me and my fellow 964 cab friends!!