993 - Targa Roof Operation Outline

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993 - Targa Roof Operation Outline From pcarworkshop Contents 1 Introduction 2 The Main Tracks 3 The Drive Cables 4 The Drive Motors & Cables 5 Two Types of Rear Gate Guides 6 The Cables and the “letting go” Mechanism 7 The Visor and Front of the Glass Roof 8 The Sunblind 9 Basic Roof Height Adjustment 10 Setting the Roof Timing Stop Points Introduction The 993 Targa top is one of the most unnecessarily complicated systems I have ever seen. A company called Webasto manufactures it for Porsche. They make OEM sunroof mechanisms for various auto manufacturers. It is a design that seems to have been created by engineer geeks with access to a shop full of machines and machinists to create whatever they come up with that day. This mentality is further noticeable in how everything seems to have been designed with no forethought for repair. One begins to believe that this may have been done to require service to be done by factory personnel only. When I was looking for my Targa I had heard about there being problems with the roofs. My mechanic said, "buy a coupe or cabriolet, the tops break and sometimes we can’t even fix 'em." But after living most of my adult life with a Targa in one form or another (a 1973 914, a 1968 911L and a 1984 Carrera) I decided to get one anyway. I found one in the color combo that I wanted and the owner said he just spent 1200 dollars at the dealer repairing the top and replacing parts. So I figured it was probably one of the safest bets I could find in a Targa purchase. After driving it about 2000 miles there was a loud clonk and the top jammed and started clicking–a sort of ratcheting noise–when I pressed the button. I messed with it, lubed it up and it would open all the way but at the last push to bring the rear of the glass up, it would jam and make the ratchet noise. Because the top wouldn’t close all the way, the wind deflector wouldn’t come down. I removed the drive motors in the back under the rear deck and discovered that the cables were stripped a bit and figured that was the problem. I ordered what is called a “repair kit” which is essentially the two glass top drive cables and a bunch of little plastic bits. The list price on the top repair kit, which is the only way to buy the drive cables, is about $1100. Sunset Porsche [1] (http://www.sunsetimports.com/) got it to me for just over $800 In buying the car, the previous owner said the dealer had done a repair, which gave me confidence. I found out later that virtually no one, at least who I talked to–other Targa owners, various dealer parts guys, independent mechanics and dealer service people–has a concept of how this mechanism works. Compound this issue with the fact 993 - Targa Roof Operation Outline - pcarworkshop http://www.pcarworkshop.com/index.php/993_-_Targa_Roof_Operation... 1 of 16 7/17/2012 5:03 PM

description

Design and Function of Porshe 993 Targa Roof Operation for '93-98 Porsche 911 models.

Transcript of 993 - Targa Roof Operation Outline

Page 1: 993 - Targa Roof Operation Outline

993 - Targa Roof Operation Outline

From pcarworkshop

Contents

1 Introduction2 The Main Tracks3 The Drive Cables4 The Drive Motors & Cables5 Two Types of Rear Gate Guides6 The Cables and the “letting go” Mechanism7 The Visor and Front of the Glass Roof8 The Sunblind9 Basic Roof Height Adjustment10 Setting the Roof Timing Stop Points

Introduction

The 993 Targa top is one of the most unnecessarily complicated systems I have ever seen. A company called Webasto manufactures it for Porsche. They make OEMsunroof mechanisms for various auto manufacturers. It is a design that seems to have been created by engineer geeks with access to a shop full of machines and machiniststo create whatever they come up with that day. This mentality is further noticeable in how everything seems to have been designed with no forethought for repair. Onebegins to believe that this may have been done to require service to be done by factory personnel only.

When I was looking for my Targa I had heard about there being problems with the roofs. My mechanic said, "buy a coupe or cabriolet, the tops break and sometimes wecan’t even fix 'em." But after living most of my adult life with a Targa in one form or another (a 1973 914, a 1968 911L and a 1984 Carrera) I decided to get one anyway.

I found one in the color combo that I wanted and the owner said he just spent 1200 dollars at the dealer repairing the top and replacing parts. So I figured it was probablyone of the safest bets I could find in a Targa purchase. After driving it about 2000 miles there was a loud clonk and the top jammed and started clicking–a sort ofratcheting noise–when I pressed the button. I messed with it, lubed it up and it would open all the way but at the last push to bring the rear of the glass up, it would jamand make the ratchet noise. Because the top wouldn’t close all the way, the wind deflector wouldn’t come down.

I removed the drive motors in the back under the rear deck and discovered that the cables were stripped a bit and figured that was the problem. I ordered what is called a“repair kit” which is essentially the two glass top drive cables and a bunch of little plastic bits. The list price on the top repair kit, which is the only way to buy the drivecables, is about $1100. Sunset Porsche [1] (http://www.sunsetimports.com/) got it to me for just over $800

In buying the car, the previous owner said the dealer had done a repair, which gave me confidence. I found out later that virtually no one, at least who I talked to–otherTarga owners, various dealer parts guys, independent mechanics and dealer service people–has a concept of how this mechanism works. Compound this issue with the fact

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that Webasto has updated parts over the years and some newer ones don’t work with other older ones. No one I spoke with knew about some of the updates.

I was originally going to do a step by step DIY on how to remove and replace the mechanism for operating the Glass Roof and Sunblind, but it is a lot, as you will see, so Idecided to do this overview instead. Procedures are covered in the service notes which are available here on MikeJ's Pcarworkshop.com In the TSBs, Parts Guides sectionfor the 993. Here are direct links: Targa Service Technical Notes Part 1 and Targa Service Technical Notes Part 2 Note: Mikej asks that you limit your downloads. Bycombining the information herein with the Targa service guides you can pretty much figure it out. If you have any problems, or other questions, PM me on Rennlist,username: "Amfab"

One problem with the Service Guide is that the glass roof drive mechanism is not designed to be replaced with the top on the car, and so the Service Guide describes theprocedure with the top off the car. And by top I mean the whole top. The Targa is based on the cabriolet body with some modifications here and there. The top is a singleunit that comes from Webasto and is bolted and bonded with adhesive to the body. Mike, who created this site is the only one I know who has attempted (successfully) acomplete top replacement, and I will leave explanations of that to him.

The glass roof drive mechanism is designed to be replaced with the top off the car. However it can be done with the top on the car, but it is far from easy. If you are goingto attempt this, or if anyone has specific questions, again, you can contact me through Rennlist, username: Amfab. I encourage anyone with a Porsche to become amember, the assistance and information you will receive there is invaluable.

In this document I left out a full explanation of how the Wind Deflector works as it is self evident to a Targa owner–once the function of the cables and Gate Guides isunderstood–how the Wind Deflector pivots up and down.

I also want to thank Mike and Robin for their contributions to the 993 community, and with a special note to Mike who was the only person on the planet whom I felt fullyunderstood, and empathized with my frustrations with the top as I undertook this project.

-Andrew MacKenzie

The Main Tracks

Running inside the two sides of the roof, above the side windows, are two large extruded aluminum channels that are bent to follow the inside of the roofline.

On this page are two pictures. One, a drawing I did of a section of the track, and an actual photo of the track removed from my car

In these two pictures the right, or passenger’s side track is shown.

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The large upright part on the outer side (left in the pictures) has eight holes where the hex bolts are. These bolt the track into the frame of the top.

The two round tubular shaped portions of the track carry the drive cables. The cables are actually long springs that act as flexible rack gears that gets driven by motorsunder the rear deck.

The Drive Cables

The top cable in the above picture is a healthy new cable. It essentially is along spring with a pipe cleaner running down the middle. The little hairs help to keep the trackclean.

You do not want to lube these cables. It will not help them to move more freely and will only gum them up while causing potential slippage against the drive gears of themotors.

The second cable down is one that has been stripped against the drive gear of a motor. The third one down shows a mild kink. This kink is enough to cause binding, whichcan lead to stripping.

Any work done on the mechanism that involves removing of the tracks or cables requires a lot of care to avoid any kinking.

The cables are the same type for the Sunblind mechanism–this is the cable that runs in the inside tube of track–and for the top mechanism, which runs in the inside tube ofthe track.

The Drive Motors & Cables

The three drive motors sit under the upholstered rear deck.

Two of the motors drive both sides of the top and one motor drives both sides of the Sunblind. It is the gear at the head of the motor that drives the cables.

Here is a photo of the three motors; they mount on a metal plate on the back deck.

The motors have a red plastic cap (seen on the top motor in the picture below) that can be removed to allow the top or blind to be moved manually with allen wrenches.These caps interlock the motor to the drive mechanism. If these red caps are damaged to the point of being unusable, the motors will not be able to engage the drive gears.Porsche only sells the motor with the caps as a complete unit (list price is in the $600 range). User "Targagr" from Rennlist discovered that Audi sells these same plasticcaps separately (part number: 895 877 899) for a couple bucks each.

'Italic text'

The photo shows the single Sunblind motor mounted and the two glass roof drive motors removed from their mounts. Visible are the three threaded mounting holes foreach motor where the bolts go to hold the motors that are removed. Care must be taken not to over torque these as they strip very easily. The mounting plate is soft steeland it isn’t thick enough to have sufficient threads. I stripped two of them, even being very careful.

The motors’ gear fits in the gaps between the two lower cable tubes. In the picture below one cable is removed. The gears on the end of the motors drive the cablesdirectly. The cable is held against the gear by the metal channels on the motor head right next to the gear.

Note the motor with the blue plastic gear on it. That mechanism is what counts the revolutions and trips a switch to stop the motor in the proper spot as the roof closes.The mechanism will pause and wait for another touch of the button to close the wind deflector, and trip the second switch. The Motor control unit reverses this process.

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The motors drive the roof and blind as illustrated below. The blind is light and needs only one motor while the heavier glass top requires two

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The mounting plate has several tubes running off of it, they are steel guide tubes that route the cables to the back of the tracks. On the opposite side of each tube thatfeeds the back of the track, there are other steel tubes that extend a bit then have plastic extension tubes that run behind the rear interior panels to hold the loose end ofthe cables when the top is retracted

The pictures below shows the two steel pipes: one for the blind and one for the roof going to the back of the track and the two plastic pipes that route the loose end of thecables from the other track behind the rear side trim panels.

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The drive cables for the blind and the glass top have plastic pieces bonded to them that carry the blind and top forward and aft. These are called Gate Guides. The picturebelow shows the largest of these Guides, the rear guide, which grabs and carries the rear mount of the glass roof

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Two Types of Rear Gate Guides

There are two types of Rear Gate Guides. A metal type and a plastic type.

My car is a 1996 (a late 1995 build). When I went to replace the cables and Gate Guides I found that my car had metal ones, I don't think they were replaced by theprevious owner, but I cannot confirm this so they may not be original. Rennlist Member Strost (Stefan) has an early Targa too (9/95 build) and it has the metal guide also.The parts I bought to replace them in 2007 are plastic, so I assume that the plastic is the updated part. No dealer parts person or service manager had any information onthis update. The only part number that shows up in the PET is the plastic one, and there is no information that I could find regarding any superceding part. Even though Iam still not 100% sure of which type was first I will refer to the metal Gate Guides from here on as the "earlier version"

The plastic guides have a raised hook that grabs the and engages the axle plate.

On the earlier version (metal) the rear axle plates in the car had a metal sleeve with a locking pin that allowed them to engage the metal gate guides. These pins would notallow the axles to work with the plastic Guides and had to be removed. Upon removing the sleeves with the pin, the axle plates seem to be the same. I thought it odd thatthe old version had an extra part that had to be removed to work with a new version part, which caused me to not be totally sure of the plastic gate guides being theupdated version, but it seems so, as the replacement updated axles currently being sold fit the plastic Gate Guides.

See Basic Roof Height Adjustment section below for more information, and to see what the axle plate with the sleeve looks like see the photo of the broken axle platesbelow

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The glass roof has metal pieces bolted to it (colored blue in the photo on the right below). Bolted to these metal pieces are metal axel/roof supports (Colored red In thephoto), that are grabbed by the Gate Guides and are carried forward and backward.

Below left is the entire mechanism that carries the rear of the glass roof, shown mounted in the track.

As the plastic Gate Guide moves forward (right in this picture) it grabs the rear roof support, which is connected to the lever mechanism. As the roof comes to the final ½inch of closing, the upper round finger (A) of the lever mechanism rides along the upper part of the track. This kicks up the little shaft part of the lever (B) that rides in thelower part of the track. This lower shaft then pivots on the hinge (C) and rides up into the curved 90-degree upward slot that is riveted to the track. This is what causes theglass top to rise to the level of the rear window glass, making it flush. At this point the plastic Gate Guide lets go of the glass top as the cable mechanism continues movingforward a few inches. At the front end of the cable is another smaller Gate Guide that then triggers the wind deflector to drop.

The Cables and the “letting go” Mechanism

Because the glass top is driven by a single cable on each side, this cable has to perform two functions, 1) moving the glass roof and 2) raising the wind deflector. Theseoperations have to occur at two separate times. To close the roof, the cable must pull the roof forward and into its final raised position. The cable must then release theglass roof and continue forward in order to flip up the deflector. This is accomplished by a complicated, delicate mechanism. Somehow it all actually works.

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The drawing is oversimplified, in reality the Gate Guide and Lever Mount have a groove and a rib to keep them aligned, the photos below show what they really look like.The top part shows the Guide and Lever Mount separated. The bottom shows the mechanism assembled how it would be in the track. Its position in the bottom part of thepicture is where it would be as the glass top is about to close (or when the top is beginning to retract - depending on which direction it is moving). When moving rearward,the angled ramp allows the raised portion to snap under the lever, so when later it moves forward the other side of the ramp can help grab and raise the lever. The Angledramp can then slip back under the lever when it is moving backwards.

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These pictures illustrate why it is so important not to lubricate the mechanism with any type of grease or even WD-40. Anything that could potentially goop up thedelicate lock and release mechanism by hindering the locking block could cause the top to jam.

If the top jams the motors can very quickly strip the drive cables. Even if the drive cables aren’t stripped beyond working, if the cable jumps a few gear teeth on one sidethe top can bind, as it isn’t being pulled forward evenly.

If the cable skips only a couple of teeth, the top will still slide and operate, but when it gets to the end of the cycle the wind deflector will not tightly close on the side thatarrives latest, creating excessive wind noise, and it will leak.

The Visor and Front of the Glass Roof

Bonded to the front end of the same cable is another Gate Guide. When it reaches the Wind Deflector, it kicks it up. The front Gate Guide does two things, it holds aslotted plastic piece called a Gate that lifts the front of the glass roof into place and then it goes on to lift the Wind Deflector.

The front Gate Guide has a Locking Block like the rear Gate Guide to engage the Wind Deflector. This one works in reverse of the rear. It grabs the Wind Deflectormechanism by the same, but reversed, Locking Block scheme as it moves forward. This pushes the Wind Deflector up. When the cable moves backwards it pulls theDeflector down, then the locking block falls, and frees the Gate Guide of the Deflector mechanism allowing the cable to move all the way back to open the glass roof.

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The front of the roof has an axle that rides in a deep angled groove (above). When the top is pulled back the axle sits in the front of the groove. As the glass roof comes tothe point where it is about to close, the top stops and the gate slides forward causing the angled groove to lift the front of the roof about 3/8ths of an inch to its closedposition

This is a photo of the cable, gate, and the mechanism that raises the Wind Deflector. This photo shows clearly how the plastic guides are bonded to the drive cables. TheGate Guide is attached to the Gate via a slot that a metal tab on the gate is inserted into. (See area denoted by dotted line. The tab and slot is also visible in the previousphoto above). All of this stuff is held together, and slides in the channels of the main track with the little plastic white tabs on either side. These are not visible when theassembly is in the track. The locking block is what grabs and releases the mount for the Lifting lever.

The Sunblind

The Sunblind is spring loaded and pre-tensioned when inserted in its mount, like an old window blind. This keeps it taught as it rolls back up.

Unlike a regular window blind it must be supported, as it is overhead. There are three rods that are sewn into slots across the blind to support it when deployed. The endsof these rods ride in the plastic tracks on each side of the car; these tracks are clipped to the main aluminum tracks described above. The ends of the rods have little plasticfootball shaped guides on them. The shape enables them to enter the track smoothly as the blind unwinds.

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There are plastic Bow Guides that are bonded to the Sunblind cables that grab the blind and pull it back. To complicate the mechanism, there isn’t simply one track foreach side of the blind mechanism, there are two.

If the blind is pulled that along the curve of the aluminum extrusion shown above in the glass roof mechanism section, the Sunblind would follow the curve of the mainaluminum channel. While this would be simpler, this would reduce the headroom so Webasto decided to make two tracks, one for the blind, which sits up higher, abovethe aluminum track and a lower one for what they call the "Pullbow".

The Pullbow is pulled by the Bow Guide and follows the Aluminum track while the blind itself rides higher in the plastic track. The other end of the Pullbow pulls theblind and the Pullbow pivots slightly as the blind rises for headroom.

In operation the plastic blind track actually rises and falls slightly as the blind rolls out. Because the track moves up and down and is very flexible, the cable also has apiece of plastic bonded to it—a Track Alignment Jaw— behind the Bow Guide to grab the track and keep it aligned horizontally.

The Pullbow is attached to the blind via a metal sliding piece that has a pultrusion (A) that inserts into a rectangular aluminum tube which is the support for the rear edgeof the blind. The other part that sticks out (B) connects it to the Pullbow to allow the blind to be operated. (Note Targa top in photo from a simpler time when men weremen and one had to get out of the car to open the top.)

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When the button is pressed, the control unit behind the rear seats “looks” to see if it is OK to deploy the blind (it will not if the glass roof is open). If the roof is closed, themotor reels the cables back. The Bow Guide grabs the Pullbow, which in turn grabs the end of the blind. The Pullbow swivels up as the blind rides up in the higher track.This way the drive mechanism for the blind can ride in the same extrusion as the top mechanism for rigidity, while the lightweight blind can ride in the higher track to givemore headroom. There is a problem however. The plastic track is higher than the glass roof when the roof is open. To prevent the track from getting hit by the roof as itopens and closes there is a bent steel “spring” inserted into the back of the plastic blind track. As the roof opens and closes it pushes on the spring and the plastic trackgets moved out of the way.

Basic Roof Height Adjustment

Height adjustment of the roof is done with bolts that hold what Porsche/Webasto call "axles" or "axle plates". These bolt to metal blocks that are bolted to the underside ofthe frame of the glass roof. In the photos below, the axles (shown in red) have plates with holes to mount them (hence the term "axle plates"). The plates are ribbed on theback and mate with ribs on the blocks bolted to the frame (colored blue in the photographs). The front axle plates have single hex bolts and the rear each have two Torxbolts holding them.

Front Axles (from in cabin, and with roof removed):

Rear axle (from in cabin):

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Height adjustment is done by loosening the bolts and raising or lowering the roof in relation to the axle plates. Do not over-torque these. The ribs in the axle plates and theribs on the blocks they attach to will hold the top from slipping, it is not necessary to tighten the bolts down as if it is simply friction between two smooth surfaces holdingthe roof up. If the bolts are over-torqued the low quality pot-metal the plates are made of can be compressed a bit by the hard steel bolts and weakened, especially on therear axle plates at the rear bolt hole. Cracks can develop here and the axle can break from the plate and jam the top. Webasto has updated the part to be a little wider togive more metal where the crack occurs, and they are the slightest bit thicker overall, maybe 1/1000th of an inch, so obviously this has been an issue. Tthe newer platesdon't look that much stronger than the older style, so again, be careful not to over-torque. Unfortunately the new ones (part # 993.562.579.01) list close to $300 each,($208 at Sunset Imports as of Spring 2008). Also problems can occur from vibration loosening the bolts - Use Locktite and torque to proper specs (see TSB below).

The picture below shows the differences between the old style and updated rear axle plates:

Note: In the PET there seem to be two types of rear axle plates. One type works for both left and right, one type has separate part numbers for each side. Noone canexplain this to me. My car uses the type that works on both sides.

There is no TSB that refers to the updated rear axle plates, but there is one for the updated front axle plates: Checking the Tightness of the Targa Roof Axle Plate refers tothe updated front ones and advises on adjustment of both the front and rear. The sketch of the rear plate in the TSB looks like an updated one. The rear axle plates areeasy to access; the front ones are more difficult to get to, the TSB says they are most easily accessed with the sunblind deployed a bit over halfway. I find opening the roofabout 14 inches or so, and unclipping the front part of the sunblind track allows me better access. Once the axle plates are replaced, then I do final adjustment with theroof closed. There is good information in the TSB along with the information about the updated front axle plates.

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Setting the Roof Timing Stop Points

These are the three motors. The rear motor is for the sunblind. The slightly more forward rear passenger side motor and the rear drivers side motor both drive the slidingglass roof.

The motors in the picture of the rear deck on the right side have metal gears to drive the cables but the right side motor also has a big blue gear. This gear is connected tothe motor drive also, and it counts revolutions. When the glass roof control button on the console is depressed the two motors are actuated, and the roof slides forward.

Once the blue gear has counted a certain amount of revolutions it triggers one of the blue stop switches (see photo). This stops the motors, and therefore the roof, frommoving forward. At this point the roof should be in its full forward, raised and closed position. When the console switch is pressed a second time the motors start turninguntil the blue gear triggers the second stop switch and stops the motor again (wind deflector in full down position.) If for some reason the blue timing gear is off buy atooth or two the roof may stop before it is actually fully closed and raised. In other to correct this the roof position and the stop position of the motor/blue timing gear mustbe synchronized to the proper top position.

Here are the steps to synchronize the glass roof and the stop timings:

1) The rear deck cover must be removed:

a) Fold down the rear seats, taking care the seat belt receptacles are folded neatly down otherwise they can poke and do damage to the rear seat upholstery.

b) Remove the four black screws and washers that retain the rear cover.

c) Carefully pull out the rear cover. The felt piece where the rear deck cover meets the window cracks easily where it meets the rear deck, take care as the cover is pulledforward and out not to snag the rear felt piece.

d) Disconnect the rear deck speakers once the rear cover is pulled out far enough to get under there.

e) Fold the rear cover down so the speaker grills are facing the back of the front seats. This will cause the rear felt piece to be facing down, so no pressure or weight canbe put on the inverted cover. This repair operation can be done with the rear deck laying in the back of the car, but is easier to avoid damage like cracking the felt piecewith the cover out of the car. This adds a lot of time to this part of the procedure though, because the seat belt bolts must be removed so the belts can be fed through theslots in the rear deck.

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2) Open the glass roof, then the close the roof until it stops the first time (what should be in the roof's fully closed and raised position.) Turn the ignition key off so theswitch won't work if it is accidentally touched. Note:The top mechanism takes quite a bit of power to operate, so occasionally start the car to recharge the battery, orput on a trickle charger. Operating the top 20 or 30 times can drain a battery that is not in the greatest of shape.

3) Remove the three bolts holding down the drivers side roof motor. Be careful not to rock it back and forth too much as it is lifted off. It is not that easy to move the gearas the motor is lifted off, but care should still be taken so the gear positions are not disturbed. Note: Do NOT remove both roof motors at the same time as this can causethe left and right cables to get out of synchronization.

4) Remove the red cap from the motor on the passenger's side, this will allow an allen wrench to be inserted into the motor gear assembly and the roof can be manuallymoved forward to the fully closed position.

5) With the allen wrench turn the gear and move the roof forward. Watch the rear axel plate (shown in red in the photo below) on one side of the car as the roof is moved

forward

The roof will get to a point where it is as far forward as it will go. As the allen wrench is turned more the roof axle plate will start to rise, lifting the back of the roof. Oncethe roof is lifted all the way the pivot continues to move slightly forward. The motor must be turned until the axle is fully up and then must be turned a bit more. This pointis critical. To find this point the motor can be turned a little more until the wind deflector is seen to start to move down. Then the motor can be backed up slightly.

6) Once it is determined that the roof is in the correct position, the motor with the blue gear can be reinstalled. Note: the bolts holding in the motors are screwed into themounting plate which is very easy to strip, take care not to over torque. If they become stripped–I stripped two of mine–the holes can be tapped to the next size threadand new larger bolts can be used as the holes in the motor casings through which they feed are large enough.

7) Replace the red caps (these engage the motor to the drive gear) and test the roofs operation by hitting the roof button in short bursts. Observe if the roof is closing andstopping at the correct position. If it is not, redo steps 2 through 6 until the proper position is obtained. Note: Do not try close the wind deflector until the stop point forthe roof is correct, because if the timing for the second stop is too late, the cables will be in the full far forward position and the drive motors will continue to turn, andbecause the cables have no where to go, this could strip the cables.

So there are the basics of how the top mechanism works, as I get to it I will add to this page more details on the top and how it comes apart and goes back together.-Andrew

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This page was last modified 20:48, 13 August 2009.

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