Convertible Top Problem

[jporter]

I have a 98 Boxster and have made several repairs, but I’m stumped by a problem with the convertible top. The top works, but makes a noise at the very end of the closing cycle. Some have accurately described the sound like a golf ball hitting the side of the car. I believe the sound is actually the result of the gears in the convertible top gears skipping at the end of the cycle. It sounds like it is only jumping one tooth as I hear a single pop when it happens. The convertible indicator light then goes out. The result is the left and right convertible top gears have to be synchronized after this happens. The noise normally comes from the left side, but I have herd the noise from both and or the right after synchronizing the convertible top gears. I currently keep this from happening by stopping the closing cycle based on the location of the convertible-top compartment lid (CTCL). Although the CTCL is tightly closed the convertible indicator light stays on as a result of not completing the closing cycle.

The top works fine when opening and the CTCL closes at the end of the opening cycle without the noise. The convertible indicator light does go out at the end of the opening cycle.

I have checked the microswitches and they all work. The B-pillar switch closes when the top closes – tested electrically. If the B-pillar switch is not allowed to close the circuit (pulled the plug), the transmissions continue to run after the CTCL is closed – multiple pops from the transmissions. I only hear a single pop when the B-pillar switch is properly connected. This was learned from a mistake not to be repeated.

The CTCL switch works. I even tested it while the top was closing and it stopped the closing cycle after a brief run time. The workshop manual appears to refer to this as the after-running time.

I would appreciate any help in solving this problem, but I do have some specific questions.

The CTCL seems to continue closing past the point needed. You actually see a slight bend in the CTCL just prior to the pop. Can the after-running time be adjusted?

I have tried to extend the parts of the mechanisms that look like shock absorbers and they cannot be extended by hand. These shock absorbers connect the CTCL to the convertible top gears. Should I be able to extend these by hand and do they provide the extra motion needed for the after-running time?

[Jonhale]

I had this on my 02 just before the cable snapped inside.

It seems the solid cable inner of the twin top cables are not so solid; They are actually wire with squared ends and can actually twist internally.

I suggest you order some new cables (before they snap) and change them.

The part numbers are in this overall thread somewhere from Jeff.

Edited May 13, 2004 by Jonhale

[mark in sunnyvale]

I'm not really sure what's causing your problem. I'm assuming you've repalced the cable, and everything is synchronized properly.

The only way I can think of making the running time shorter is by extending the switch on the motor so it gets actuated sooner.

Ok, this is a half-assed idea and I haven't tried it myself. So please take it at it's value. I would suggest that you place something on the edge of the switch so that it hits the clamshell sooner. Do a temporary mock-up, if it works I'm pretty sure you can come up with a more elegant solution. My $.02

Edited May 13, 2004 by mark in sunnyvale

[Tool Pants]

http://www.renntech.org/forums/index.php?s...st=0entry1024

What is the history of the top? Have repairs been made? If so, what was the problem and what parts have been replaced. Have the cables been replaced.

I do not know of any way to adjust the run time. That is a function of lever switch above the top motor and the top relay/control unit.

I think the black push rods that look like shocks have a spring inside which provides the tension to hold down the clamshell. There is no adjustment. If it is defective then it is replaced.

[Alienz]

I have the same problem. I actually spent 4 hours today trying to fix the problem. I put the top in the service position and ran the cycle, i heard the poping from both sides. The reason you hear the noise is because when the transmission comes to the end of the cycle there are no more teeth so you hear the snap back because the strut pulls it back. I think I know what's wrong, it is not the transmissions, it's the motor. The motor is not stopping where it is supposed to. It keeps going for few more seconds before it stops and the top light goes out. That's the only explanation I could come up with. Sometimes my top goes a bit crazy (because one of the cables comes out) the the plastic pieceon the rod breaks. Two plastic pieces have broke so far (one today) on the passenger side. There is also something weird that happens towards the end of the cycle, when the button on the motor is pressed, I stop pressing the convt top button then press it again and when I do this the top compartment goes up a little bit then comes back down.

Does anyone know the purpose of that button on the motor?

[mark in sunnyvale]

The up a bit and down again behavior is normal. All tops do that, or at least mine does.

The switch signals that the clamshell is closed, it keeps going to seal.

Like I suggested above, I think if you shim something between the switch and the clamshell, the cycle will terminate earlier. Good luck.

_Mark

[jporter]

Thanks everyone for the replies and suggestions. I was out of town yesterday for a meeting. I drove the Boxster and the drive home on the back roads was fantastic – top down, 72 and stars in the sky. I had to turn the radio off so I could hear that beautiful sound coming from the back of the car.

I will work on the suggestions this weekend and let you know the results. As far as the known history goes, it starts when I bought the car from the widow of the previous owner. She didn’t know where he kept the records and I wasn’t up to pressing her to look for them. I was told that she is glad that the car was restored to reasonably good working order – a passion of her husband – and I think she will send the records if she finds them.

Thanks again for the suggestions and I will let you know how they work.

[Tool Pants]

Ok, I had assumed you tried some repairs to the top and then the noise started.

Determine if you have the original unreinforced cable housing. Then remove the clip on the motor for each cable and see if you have about 3/4" of the square end sticking past the metal end. There are pictures and instructions on this board.

[jporter]

The top did not operate when I got the car. The problem was related to the convertible-top lock switch. I believe it was a slightly different problem than the microswitch failure people have discussed here.

There are two “conductor bars” (small strips of steel) that are on top of the lock unit. These are visible when the lock unit has been removed. They connect the left side of the lock unit to the microswitch on the right side. When electrically testing the lock unit off the car, I found that it worked every once in awhile. I determined that this was related to how I was holding the lock unit and that’s when I noticed the small break in the solder joint at one end of one of the “conductor bars”. I repaired the joint with new solder and it has worked since then – that’s when I started to hear the noise.

Thanks again for the help. I know I have at least ¾ on the right side since this is the side I remove to synchronize the two sides. I will let you know what I find on the other side.

[Alienz]

**** it! One plastic piece broke again (driver's sode). Man I'm getting sick of this. If they sold this plastic piece seperately I would buy a 100 of them. The only one I could find is the metal one.

[jporter]

I pulled the cables and they are the old style. The square ends extend about ½ inch on both sides. Although they are not as bad as the old cables shown in the other threads, I plan to replace them – better too soon than too late. I’ll keep looking for other reasons for the noise.

Hope I get a fix before I break a red ball - sounds like they are in short supply

[jporter]

The following should (if I know how to post images) be a picture of the ends of the flexible shafts.

[Tool Pants]

Your cables look almost ok, but a bit too short. The square ends could stick out longer. You got me. If I had your car this is what I would do.

Put the top in the service position and disconnect the red plastic joints. Have someone operate the top switch while you watch the clamshell open and close to see where the noise is comming from. You have to watch out that as the V-levers move the red joints do not get hung up on something a break. If you have 2 extra helpers have them hold the joints clear while the clamshell is operated.

If it was my car I would replace the cables, since with a 1998 you should do this anyway.

Then report back.

[jporter]

I tried to trip the switch earlier per Mark’s suggestion, but the motor continued to run until the pop sound. The image on the left is the end result of building up the area on the clamshell that contacts the switch lever. The material shown is about the maximum that could fit between the clamshell and the housing of the motor. I monitored this by looking under the skirt of the convertible top – not as exciting as it sounds. The switch was actuated earlier, but the clamshell continued down until it made the sound referred to earlier.

I then added the additional foam shown in the image on the right. The foam did actuate the switch upon contact and then compressed when it contacted the housing of the motor. I was surprised that this did not stop the motor early enough to stop the noise at the end of the closing cycle and this could be the result of not having enough room to actuate the switch earlier. Regardless of the outcome I think it could provide a clue to how solve the issue. Thanks again for the idea.

My next effort will be to follow Tool Pants suggestion and get a better fix on the location of the noise. This will have to wait until next weekend and I will post the results.

[Alienz]

I think the motor is bad on your and my car. All the timing is perfect, the top comes down and goes up so there is no reason for this poping sound unless one of the components is broken. Maybe the switch in the motor is busted. I'll try working on it today and see what I come up with.

[Tool Pants]

Try a relay/control unit from another 1997-1999 Boxster. It is far more complex than a simple relay.

When the clamshell is is going down and hits the lever on top of the motor the motor continues to run for a second so that the black levers can pull it down tight.

A German guy opened a 2000 relay to modify it and it is like a little computer in there. There must be something in the control unit that tells the motor to run that extra second, like it tells the windows to drop.

[Alienz]

Do you know the location of this unit?

[Tool Pants]

Look above the fuse box and you will see the relay tray. The top control unit is twice the size of the other relays.

Pic is Henry's 2000 tray which has been pulled down for a mirror install. On a 2.5 it is black and does not have a white sticker on it.

The unit just pulls straight out once you reach up there with your hand.

[Alienz]

Thanks! My friend talked to a Porsche mechanic in Albany, NY and here is what he told him: they've had a lot of problems with the early tops because of the cable problem and software (?) that regulates the top motor. He siad that most dealers don't want to mess with the old-style top which is why they charge $2k to replace everything. He'd seen the problem we're discussing before and that's what he suggested: buy a spring and some appoxy, measure the distance the top compartment travels when the motor lever is pushed down. Cut the spring the same length as that distance then attach it to the compartment. This will takecare of it. He said that he'd done this before on other Boxsters outside the dealerships. Hope this helps.

[Tool Pants]

The spring thing is new to me. Would like to see a picture some day.

I'll ask Peter at my dealer if he knows about this noise. But, like Alienz says, they just replace everything and do not mess around with trying to fix what is there.

We do not have any local cars with this noise or I would try the relay swap and see if that is the problem. I have 2 relays and both work fine.

[jporter]

I had some time to work on the top issue. I measured the “after running” time for the closing and opening cycles. I used a string to trigger the clamshell switch and a camera to record for time measurements – shown below. The “after running” time for closing was normally 1.15 seconds with a couple measurements to 1.20 seconds. The “after running” time for opening was normally 1.00 seconds with some as low as 0.40 seconds. This could be why the opening cycle works. I do not know the reason for the short times, but they could be the result of being near to the point that the B-pillar switch changes. I found that if the clamshell switch was held when opening the top from the closed position that the top stop as soon as the B-pillar switch changed. This also happened when closing the top from the open position.

Another reason for the opening cycle working could be the additional load to compress the top at the end of the opening cycle. This could slow the motor and result in less travel at the end of the cycle. I will look into a simple circuit to slow the motor during the closing cycle. I will post the results when I try this.

[jporter]

I also looked into modifying the relay to change the “after running” time. The 98 relay is also very complex as shown in the images below. The images show the top and bottom views of the relay out of the case. I plan to show the images to a friend who knows controls. I will post any information I learn about the relay.

[jporter]

I have come up with a solution for the top problem. Although it is not a simple fix, it does work and the total cost for parts was about $25.

A mciroswitch senses the location of the left side top transmission. This is used to stop the drive motor for the top. An electrical circuit comprised of a relay and capacitor opens the power line for the motor for about 2 seconds. This is long enough to keep the power off until the “after running time” is over and the top indicator light turns off. The power line is then closed so that the top can be operated. The electrical circuit also includes a resistor and diode to protect the car’s electrical system from a possible discharge of the capacitor.

The components are located such that they are out of the way of moving parts and the top when it folds into the compartment. The following images show the components and locations.

I will continue to look for a simpler solution and will post it if I find one – this will not be a priority effort since I have a fix that is working.

[Dougman]

I've spent a fair amount of time and have come up with my own solution to this same problem. My top also "popped" loudly at the end of the close cycle. Often on one side only, with the resulting mis-timing left to right as an outcome. Not much change to timing if it happens once, but over time, the tonneau cover definitely starts to warp L-to-R.

In my opinion, after getting to understand how this system works, the problem is that we are running out of gears before the top cycle is complete. If the sprung struts (the black ones that move the tonneau cover) were just a bit shorter, I think this would be the ideal solution: the switch above the motor would be actuated earlier, and the closing cycle would be complete while the worm gear in the transmission was still in contact with the gear. There is so much adjustment in the top struts that I don't see any problem with keeping the top and tonneau coordinated even with this approach.

In the meantime, I took AlienZ advice and grafted a spring onto the top of the motor switch, so the tonneau cover actuates the switch earlier. It does need to be a spring because once the tonneau is closed this is compressed. I also found a small block of foam works too; I velcro-d it onto the tonneau. In my case the spring sticks up about an inch and a half higher.

The only downside is there is a bit more rattle when the top is down from the tonneau--the struts are not as compressed, so this makes sense (hence my other conclusion about short struts).

I am going to order some used tonneau struts from Silver Star Recycling (great place), and cut and weld them a hair shorter. I'm confident this is going to be the best fix; I'll let you know after I try it.

[jporter]

Hope it works as it would be an improvement to have a simpler solution.

I plan to relocate the relay circuit with the other relays up front in the meantime. Although the current solution still works, it would be helpful to access to it if there is a problem and the move would keep it out of the weather.