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Re-aligning the 993 convertible top
Replacing the drive cables

 by Bill Noble

This article is copyright W Noble, Oct 2002.  Permission is hereby granted to display and  print this article for personal non-commercial use only.  For permission to reproduce in quantity, or to use for commercial purposes, please contact the author at william_b_noble@IEEE.org .

It is really annoying when your convertible top jams half way up (or down).  Here is what you do to fix this.  

1. The quick fix, so you can keep driving - this is what you usually do first because the top will inevitably jam when you lower it while stopped at a traffic light, or in a parking lot.  Remove the black plastic cap that covers the 19 mm bolt on the jammed side, and loosen the bolt two or 3 turns - DO NOT REMOVE THE BOLT.  You can loosen both bolts if you are not sure which side is jammed, and then move the top by hand, or you can just loosen one bolt and then raise and lower it electrically (but help it out by hand so you don't break anything).

2. The complete fix - so it will work electrically again (until this event recurs).  You must start with the top up.

a. remove the cover over the motor.  The motor is located behind the rear seats.  Turn the black plastic screw in the center of the cover half a turn, then fold and lift out the cover.

Here is the screw.

Here is how you fold the cover to get it out

b. remove both clips that hold the cables to the top lift motor.  Here is the motor, the clips are the gold things on either end.  They can be lifted straight up (by hand) to remove them - you do not need a tool.

c. Presuming you only loosened one bolt to get the top working, raise the top about 10% of it's travel, so that it is partly open.  Do this using the electric motor in the normal way.

Then, pull the cable from the good side out of the motor.  This will prevent the top from moving.

Now,  remove the loose bolt entirely (and catch the two washers, one copper, one steel that are behind the top arm).  You will see a slot that receives the tang from the top arm (when you move the arm out of the way) - see this picture

Put the top arm over the slot and note where the slot is supposed to be for it to align.  Then, move the arm out of the way and using the electric motor, either raise or lower the top (note, the top is not moving, only the slot is rotating) until the slot is properly aligned.  Note - if the slot does not rotate when the motor runs, then you may have a broken cable, or the gears may have become disengaged (the large gear that drives the slot is only a partial gear) - to test if the gears are disengaged you need to see if you can rotate the slot - if you can, they are disengaged - rotate it until it stops and then run the motor again.

Once the slot is in the right position, replace the washers (copper goes closest to the gear/slot, then the steel, then the arm, then the 19mm bolt and washer).  Tighten the bolt.  Now, raise the top (or lower it) just a bit until the two sides are aligned with each other.  Be careful not to go too far.

Once the top is in alignment, then reconnect the other cable and reinstall the clips.  Then replace the carpet/cardboard  and rotate the screw half a turn.

Replacing the Drive Cables 

You will find, if the top jams more than once or twice, that it becomes a recurrent nightmare - about every third or fourth time you raise/lower the top it jams.  This is both distressing and ruinous of your enjoyment of a nice car.  The cause, at least in my case was that the drive cables actually get shorter.  This seems strange, but if you think about it, the cable is really a bunch of steel wires, and if you overload it (which happens when the top is jammed), the wires twist a bit, and when you twist these wires the overall length of the cable becomes shorter.

So, how can you tell? The drive cables should each protrude 1/2 inch (1 cm) beyond the end of the metal bell at the end of the housing.  If there is significantly less than this amount of cable protruding, then you have a problem.  I found that one of my cables was actually almost flush with the housing end, and the other protruded 1/4 inch (1/2 cm) or less.  

You might be able to fix the cables by pulling on them, but I wouldn't try this.  You can certainly fix the cables by buying new ones from the dealer for about $320 (update, July 2009, Dealer price $341, cheapest web price (partsgeek.com) was $233.02) - there is a left cable and a right cable.  The right cable is more expensive, and it has a gold colored wire in it, whereas the left is all just plain steel colored.  You can identify the right side cable because it is wound in the opposite direction of the left side, and it has a brass wire wound around it (it looks like a brass colored stripe).

Getting the cable assemblies out

To get the cable assembly out, you have to remove the gear box and unscrew 4 screws.  I have not taken pictures of this, so you will have to do without visual aids and follow these instructions.

1. remove the cover over the electric motor (as shown above). Of course if you just checked the lengths of the cables this cover is already removed.  Also disconnect the cables from the motor as described above.

2. remove the carpeted panel that covers the gear box.  This is the panel pictured in the very first picture of this article.  It is held in place by two screws, one is below the speaker, towards the front of the car, and the other is at the very back of the panel.  The one at the back is covered with a plastic cover that snaps off with finger pressure, the one below the speaker is not covered.  Remove the two screws and pull the panel to the rear of the car so that it pops out from the channel that holds the front of the panel in place.  Presuming there is a speaker, as shown in the picture, unplug the two spade connectors to the speaker.  These connectors are different sizes, so you will have no problem putting them back where they belong. 

3. Remove either the bolt with the 19 mm head (see quick fix) or (the method I prefer) remove the allen-headed bolt that connects the arm from the gear box to the frame of the top.  Removing the allen-headed bolt simplifies alignment when you reinstall the gearbox.

4. Remove four bolts with 10 mm heads that hold the black colored gearbox to the body.  Each bolt will have a spacer on it - the space lies behind the gear box and holds it out from the body - one spacer is longer than the others.  It's pretty obvious, but be sure to notice where the long spacer came from so you can put it back in the right place.

5. Flip the gear box 180 degrees so you can see the back.  You will see four phillips headed screws with washers underneath them.  These screws hold a black metal cover in place.  The cover holds the cable jacket in place and also covers the small driven gear.  Remove these four screws and lift off the cover.

6. lift out the cable housing and the white plastic rectangular part that comes with it - this part conceals a worm gear affixed to the end of the drive cable.

7. Pull the white plastic part and the worm gear and the attached cable out of the housing and put it aside.  Set everything down on some clean rags (so you don't get grease on your car).

At this point, if you purchased replacement cables from the dealer (I did not) you may be done.  I believe (but have not verified) that the replacement cable comes with the white plastic part and the worm gear attached to the end.  Just insert the new cable into the housing, press the gear back in place (being sure that the small metal button is in its proper location at the end of the white plastic part), and proceed.  If my guess about what you actually get from the dealer is incorrect, read on and follow the steps that are applicable.

If, like me, you are annoyed at the prospect of paying $300 plus for $10 worth of cables, then follow the next series of steps as well (be sure to read my Sept 2003 update).  If you purchased cables from the dealer, skip ahead to step 20.

8. The parts put aside are a cable with a worm gear and a white plastic assembly that is the bearing for the worm gear.  There is a thrust bearing which is a 3/16 inch (.2 cm about) disk that sits in the very end of the white plastic assembly.  DO NOT loose this little part.  Frequently when you disassemble the gear assembly, the little thrust bearing will remain behind in the main gearbox.  Be sure you know where it is, you will need it for reassembly.

9. the white plastic part consists of two pieces, a U shaped piece that holds the "front" end of the worm gear (the end without the cable) and also holds the thrust bearing, and a larger "L" shaped piece that makes up the top of the assembly and the rear bearing for the worm gear.  Gently pull the front white plastic piece off the worm gear and put it aside.

10. The worm gear and cable can now be pulled through the L shaped piece.  I found I had to pull pretty hard to get the gear to separate from the L shaped piece.  BE CAREFUL to not break this piece.  When you do get the gear separated, put the L shaped piece aside.

11. you now have a worm gear with a drive cable glued into it.  You need to break the glue joint without damaging the gear.  I did this with a gas stove.  Wipe the excess grease off the gear and cable. Hold the gear with pliers (being careful not to damage the gear teeth).  Heat the gear where the cable enters with the gas flame until you see bubbling at the joint where the cable enters the gear.  Pull on the cable with another pair of pliers.  If the cable does not come out when you pull hard, heat the gear some more.  You do not have to (and should not) heat it red hot, just hot enough to weaken the glue.  Overheating may affect the heat treating of the gear.

12. Once the cable is out, cool the gear (drop it into some water) and then clean it up.

13. Make a new cable.  To do this, you need to go to a place that has a selection of drive cables.  I went to a marine supply store (if you are near Los Angeles, I went to Coast Auto Marine on Lincoln Blvd).  You may also wish to bring one of the housings with you to the store (I did).  You will find that the cable housing is glued in place - you will need to lift the carpet and pull the housing out without damaging the rubber material it is glued to.  Beware that the new cable needs to have the wires twisted in the same direction or it won't last very long.

If you bring the housing, get the fattest cable that will fit through the housing and turn freely.  Have the store swage the ends square, and make sure that the ends fit into the square hole in the gear (check both ends).  I had the store make the cables about an inch longer than the old cables, and then I shortened them as required upon reassembly.  You could measure the length of the housings, and then have the cable made 1 inch (2 cm) longer if you prefer.  I also removed the lift motor (4 nuts and one electrical connector) and both cable housings so I could measure and assemble everything away from the car to be sure it all fit correctly.  You may choose not to do this if you like.

If you have to trim the cable, you will need to braze the end first or it will unravel as you trim/grind it.  Brazing and then filing it square again ought to make the ends stronger too.

14. Use red Locktite (or equivalent) adhesive to glue the cable to the gear.  

15. Reinsert the cable/gear into the L shaped piece and reattach the U shaped piece.

16. Grease the cable and gear (I used black moly grease), and reinsert the cable into the housing.

17. Put the thrust bearing into the white plastic front bearing, and press the gear/bearing assembly into place in the gear box, and reattach the cover with the four screws (with washers).

18. Check that the cable protrudes about 1/2 inch (1 cm) from the end of the housing, and reattach the cable to the motor with the small clip.

19. If the cable seems too long, disassemble, shorten by grinding or cutting the end, and reassemble.

20. When it all fits back together correctly, tighten the phillips screws and then reattach the gearbox to the body using the bolts with the 10 mm heads.  Be sure to put the long bolt and the long space back in the proper location.

21 Reattach the arm you detached in step 3.

22. repeat if required for the other side.

Note that if you are doing both sides, and making your own cables, I'd recommend pulling both cables at once to save a bunch of extra back and forth between your work bench and the car.

23. When done, align the left and right sides, if required, as described in the first part of this article.

Sept 2003 Update After all that, it turns out that the right side cable is wound "backwards" from the way that most drive cables are wound, so my rebuilt cable lasted less than a year.  In the end, I bought the right side cable assembly from the dealer for $175 and changed it.  The kit came with a new brass drive gear, a new cable with the worm gear attached, and a new housing.  I changed the whole lot and saved the old parts for spare.  If this too does not last, I'll update the DIY again." -- July 2009 update - left side failed (made itself too short) earlier in 2009, so I'm replacing it again - 6 years, maybe 50 to 100 cycles.  I think next time I will eschew the powered convertible top.

This page updated 07/09/2009