Power Top in Manual Mode

[RichardBartlett]

Power Top in Manual Mode

I recently purchased a 944 S2 cabriolet that had the power top “converted” to Manual Mode.
The conversion was done by removing the plastic caps behind the drivers and passengers seats in the Side Trim Panel (941 555 021 10) and loosening the 19mm bolt (4 turns) to disengage the Operating Lever from the Transmission and replacing the cap. Top works manually.

The motors functioned but the top does not move.

As a test, the Operating Lever bolts were tightened to engage the Transmission and the motors were run. Again lots of sound, but no movement.

Since I am retired and have a lot of time on my hands, I decided to disassemble the top down to the motors and try to troubleshoot the problem.

After disassembling the rear part of the top, to get to the motors and cable system, the following was discovered:
1. The cables inside of part #911 561 108 66 and #911 561 107 66 were 11 mm short, so the motors were turning the cables, but the cables were not turning the Transmission (911 561 045 68).
2. After disassembling the Transmission and Planetary Transmission, I found these parts to be well engineered and almost indestructible. The grease needed to be replaced, so I cleaned the gears and replaced the grease with Coastal Industrial Moly EP Grease (purchased from Wal-Mart)
3. Operation of the Transmission and Planetary Transmission (911 561 103 65):
a. The motor spins the heavy duty speedometer cable in its case (911 561 107 66) turning a worm gear at the Planetary Transmission.
b. The worm gear turns a 2” gear, increasing torque
c. The 2” gear turns a ¾” gear thru the Planetary Gears at a ratio of 4:1, increasing torque.
d. The ¾” gear turns a 6” machined gear increasing torque, to operate the top.
e. The 6” gear is a half gear, if you only are going to use half the gear to operate the top, why not save the weight and us half a full round gear.
f. The 6” gear is connected to the Operating Lever via an indent in the gear casting which matches a corresponding bulge on the Operating Lever.
g. When the hex head bold (19mm, M12x30) is tightened the Operating Lever and the 6” gear become one unit, which can raise and lower the top.
4. For my problem, the fix was to go to a local speedometer shop and have them make up 2 longer heavy duty speedometer cables. The cable should be 38 ¼” long. This length will leaves small amount of distance at the end of the cable so it can move back and forth about 1-2 cm’s when under load. Because of the high torque load, a thicker cable is necessary, so take the old one with you.

So far I was working with the Driver’s side transmission. I knew where I set the 6” half gear (tooth #6) was positioned, but I did not know where the gear on the passenger’s side was positioned.
After reassembling the Driver’s side parts, I proceeded to remove the passenger’s side Transmission. Again, cleaning and greasing all the parts, planetary gears, etc. and setting the Passenger’s side 6” gear on tooth 6, there by exactly matching the Driver’s side 6” gear position. (this synchronized the two sides of the top).

I assembled the Passenger’s side parts and tested he action of the top.
1. Ignition key in position 1 of the ignition..
2. Doors shut
3. Windows up
I carefully pushed the up button for the top, by holding it for about 1 second to see what was happening. The top slowly rose, both sides synchronized together to the fully closed position.

I adjusted the two micro switches (911 63 037 00) so the top stopped at the windshield coming up and compressed above the rear seats when coming down.
Slowly ran the top up and down a few times to check operation and I was finished.
It took about 16 hours to learn how to repair the top and troubleshoot the problem of a non-functioning automatic top.

[jeff968]

Nice job!!! A manual top 944 or 968 cab is a sure sign of an owner putting off dealing with a problem and to me, it is a red flag about the care of the car in general.

[flash968]

not at all. it is frequently a sign of somebody wise enough to know that the design is weak, and prone to failure. there is a reason bmw abandoned this design. porsche did too.

it is, however, a sign of an informed owner smart enough to avoid ruining a top due to that design. i have put both of my cars in manual mode for exactly that reason, even though the mechanisms and motors "work" just fine. i would point out that nobody i know of takes better care of their cars, and specifically their tops than i do. heck, i replace the top when it shows any signs of wear or fading of the stitching. in fact, i am just about to do that to the white car for that very reason.

a top in manual mode is often a sign of somebody who actually takes care of the car, not somebody ignoring it or delaying a repair. almost everybody i know with a convertible 968 is in manual mode, as they have learned what it means to ignore the wisdom, often the hard way.

what is a sign of somebody ignoring their car is one with a faded headliner, because they were too lazy to put on the boot cover, as it should be installed every time you put the top down.

that being said, i applaud the effort for getting it back up and running. now, put it back in manual mode and rest easy.

[azbanks]

I would rather deal with the top in manual mode than deal with replacing a broken bow(hard to find and big $$$).

[flash968]

exactly! it's not like the power top is really a power top anyway. you have to stop half way, push down on the window, then lay a towel down on the window (if you don't want to see it crease or get scarred), then put on the boot cover. all in all it takes about 2-3 minutes. i was really bummed when i found that out. after 25 years of cars with manual tops, i was thinking i was finally going to have a power top. wrong!

not sure what's wrong with porsche, but even a cheap mustang has a full power top, AND a glass heated rear window.

even if you were willing to deal with the shortcomings, you still have to deal with a frame that is known to break, motors that fail, and cables that snap.

we got screwed.

it's easier, safer, and a whole lot faster to stay manual.

[marko]

Thanks Richard, thats a great write up. I'll be back to re-read your post when I find some time to work on mine.