pingwrx

I’m a new 1996 993 C2 Cabriolet owner and I’ve been REALLY enjoying the new ride. The other day my automatic cab top stopped working, I guess this was inevitable. After reading the threads and DIY on p-car.com, I took the transmission apart and realigned the gears and cables and had it working again. But fearing future issues with the auto top and reading recommendations from Rennlisters, I converted the top to manual and used the cabriolet button in the center console to operate the locking latches. Everything was fine and had the top down ever since.

Well, yesterday I wanted to put the top up, as it was a little chilly in the morning. I manually raised the top to the edge of the windshield, and then I hit the cabriolet button on the center console to lock it down. I hear (and see) the two latch motors operating and can see it pulling the top closed, however before locking it down completely, it stops. The locking procedure wasn’t complete and I can feel the top a bit loose on both sides. I rerun it few more times with the same results; it just will not do a complete lock down always stopping approximately half way. I manually locked it down completely to see how much it still had to go and it confirms that locking latches were only at half way. Also during these tests, the operation of the locking latches was intermittent when depressing the cabriolet button, sometimes it worked and sometimes nothing, except a faint clicking noise. So I’m thinking the issue is either the two-roller micro switches on the cabriolet top going bad or the cold soldering in cabriolet controller box losing contact.

To test the two roller micro switches, I duct taped the two switches down, and with the top down, so I can see what the two latch motors more clearly, I would then depressed the cabriolet button on the center console. While doing this I can see the two latch motors operating fine, moving both way and moving the proper amount of distance (not stopping half way).

So my questions are:

Why are my locking latches only working half way when trying to lock the top to the windshield frame, but the latch motors work fine with full range of motion while testing it with the top down and the two micro switches taped down? Can this be a sign of bad micro switches or is it the cabriolet control box soldering issues as noted in past threads? (By the way the top latch motor recall was completed by the previous owner.)

Any help and recommendations will greatly be appreciated…thanks in advance.

sdcabrio

Ping, I am in the same exact situation with my cab. I love having the maual top, but have been puzzled by the intermintent working of the electric latches.

I have searched and searched threads and I can't come up with anything.

What I have found, is the outside air temperature at the time maybe is connected to the problem. The latches seem more likely to not work when its cold out. Air temp. could have effect on controller box conections and the top fabric is tighter/smaller when cold.

I have gone to put top up on a chilly morning, had latches not work in garage, but then after getting to work they latched up fine. I had heated the inside of the car using the floor vent (near controller box). Maybe warm/cool air effect controller box, I don't kow. I plan on taking the box out and having a friend who is great with that kind of thing re-solder everything inside.

Please post anything you learn.

pingwrx

Today, I converted my top back to auto mode to check to see if this solved anything. And this is what I found out, when I close the top by holding the cab button down and as it hits the window frame the locking latches kick in and locks it down completely. This is without me guiding the top to the windowsill with my hand; I just let the edge of the top fall naturally to the windowsill (sometimes slamming down a bit). But, if I guide the top, with my hand, to the windowsill to “gently” meet the windowsill, the latches will not operate. (This method would be similar if it was in the manual mode. I would bring the top to the windowsill and gently lay it down before latching it down). In this case, I reverse the top; about 3 inches and hit the cab button again so the top would hit the windowsill with some force. And in one motion, the top would hit the sill then the locking latches will kick in and lock the top down. So my thoughts are since the hitting of the top against the windowsill is triggering the latch motors, it must be the two rolling micro switches that are not working properly. Am I on the right track?

PG993

ping

I've recently had some intermittent issues with my cab top and still not resolved. To address your question wrt micro switches I don't think they are responsible for your problem. I think their only function is to tell the computer that the top is on the sill and its time for the latching motors to activate. I don't think they have anything to do with stopping the latching process in any way since they are in the electronically closed state during the entire process and stay electronically closed. (as an aside, I still cant figure out how the computer knows to stop the latching process). Only when you lift the top and the micros go into the open state again after unlatching is complete, is a signal sent to stop the latching motors.

Since your latching process starts OK and the micros stay closed throughout, then the latching motors should run to completion unless something else is telling them to stop half way down. I suspect that the computer module is the culprit, just as it probably is for me.

I'm no expert so don't "quote me" on these comments but I hope to learn enough from these posts to solve my problem also.
Paul

hn

I think that might be your problem. You left the top down too long and then raised it up on a colder day. The fabric needs some time to stretch. If you leave it up for a few days your problem might just go away. It's my guess.

Most people don't leave the top down overnight for this reason.

cpdjfd107

The cab top controller is an easy fix. It is a pain to get to. You have to lay down on your back on the drivers side floor with your feet and legs on the seat. Looking up under the dash the controller is behind the VDO box. Once you remove the VDO, and undo the cab top controller, chances are you will see some cold solders that aren't making the proper connection. I just got a cheap solder kit and just melted the solder that was already on there back together to make a good contact. In a few spots I added some solder. Even though this box is secure when going over bumps and potholes etc, this could place extra stress on the solders, so when installing I put a 1/4 inch piece of felt (cut otto the size of the controller box) and placed it between the VDO and cab control box. Screwed everything back in and all was fine. I would still make or keep the top in manual mode and just use the button to release and lock in to the header latcjes above the windshield. That way you don't have to worry about any of the microswitches in the back.

pingwrx

Hi Chris, thanks for the input I may have to pull the top controller out this weekend and check it out. But my main question is how come when it's in AUTO mode the locking latches work fine and the top is closed nice and tight, but when it's in MANUAL mode the locking latches only lock half way and the top is not clamped down completely? Could this be the top controller issue?

BTW: Chris, I was the person in Oregon who spoke to you on possibly buying your C4 Cabriolet. As you can see I found one.

cpdjfd107

When it is in manual mode you need to make sure you pull down on the top enough to pull the pins in the slot on the header on windshield frame. ust laying it up there wont be enough the motor wont catch the pins. I usually put the top up so it rests on the pins in the slots then get in the car, sit in drivers seat with windows open and reach on each side of the roof and pull down evenly at the same time so it pops in the holes a little more then turn key to battery and press the top up button. If I remember correctly there are micro switches on the header motors also and if not making the correct contact then the roof button wont pull it down and latch it in. I assume the switch under your e brake is working, e brake must be in up position for roof to operate BTW. Looks like you found a nice cab, very nice list of mods. I bought a C4S so I don't have to deal with any of this convertible top stuff Good luck with your car enjoy it, open top motoring at it's finest!!!

Sean Hamilton

Or broken latch gear teeth, which throws out the sycro limit stop on the internal latch motor mico's. Here's some good discussions:

Cab Top Front Latch Motors 1.

Cab Top Front Latch Motors 2.

Latch Gear

The hidden Black Box

BTW, what is your Cab Top Warning Light telling you. Mine is manual, and will fully close snug at the press of the button after gently resting the top down onto the windsceen ... and warning light goes out ..... all thanks to a lot of Micro Switch fiddling.

Good luck.
Sean.

pingwrx

Sean,

Thanks for the links, I'll take a closer look at them, and will probably remove the top controller box this weekend to take a look. As for the cap top warning light, no issues there, it goes on and off like it should (and when it's suppose too).

Sean Hamilton

Even when the top has not fully closed, the light goes off ? The micro limit switches are signalling the controller that the top is closed when in fact it’s not and the controller is therefor extinguishing the warning light ?

The internal latch mechanism micro’s (which are activated by the rotating shaft cam) limit the rotation of the latches, regardless of actual closing position. I wonder if you reset to manual mode, you had someone assist - push down on the top at the windscreen as you press the cab top button, would it then close properly ? Hood alignment – the two locating pins at the windscreen corners. If, over the years they have misaligned (easy to check & see this as you rest the hood on the windscreen) then they can set up quite a resistance, the pins scraping at the sides of their recesses especially when gently resting the top down by hand, leaving the top not quite positioned but sufficient to activate the micro switches which in turn activate the latches …. but all too early. In auto mode it’s all pretty rough, aggressively slamming the top down - brute forcing the pins thru.

Anyway, the fare we pay for top down motoring. I’m hoping it’s not broken gear teeth, for you. That is one mongrel of a job !!
Sean

pingwrx

Sean,

Thanks for the additional info. I checked the micro switches in the back located on the rotating transmission and tried adjusting it and it seems to be working fine. When it was in the manual mode, it looked like everything was lined up correctly and my friend held the top down as I pushed the cab button to activate the latch motors. And as I mentioned previously the latch motors ran, but didn’t run a complete cycle and stopped before closing down completely, only about half way.

Another question is, in the auto mode, as I'm closing the top, what tells the system to switch from the open/closing motor to the latch motors? Correct me if I'm wrong, but I'm assuming the system works this way…first the back micro switches tells the system that the top is at the closing limit and tells the open/close motor to stop, and at the same time the rolling micro switches near the windshield top gets triggered that tells the system to go ahead and activate the latch motors. Am I on the right track? And all of these signals are sent to the controller box, correct? If so, I’m guessing it’s got to be the controller that is causing these intermittent issues. I will be working on it this weekend, if I get motivated. I will post what I find out.

pingwrx

So I spent the day today removing the top control module (boy I never knew my body can still get in those positions…wow ). After removing the control module I took it apart looking for cold solder. Under a magnifying glass, I did notice some of the soldering was starting to separate. So I tried to solder as carefully as possible, as I’m not experienced at soldering, a rookie at best. I hit about 4-5 of the joints that looked the weakest and put some extra solder on it, but didn’t want to carry away as I didn’t want to make it worse with my inexperience soldering. I reconnected the module and to my surprise……….nothing………...just some clicking noises……….YIKES….I just made it worse! I immediately removed the module and took it to a local electronics shop. Luckily it was slow and the repair person was able to look at it immediately. He mentioned there were a lot of cold solder joints that was starting to separate. He also said he would look at all the soldering joints and fix the ones he thought that was necessary. After about an hour of his time and $15 later, I took the module back home and crossed my fingers. I reconnected the control module and put the VDO box back and started the car….I then hit the cabriolet button and viola…it worked ! It went up and down, latched it down, unlatched it and everything seemed to work fine. So to test it further I converted to the top to manual mode, brought the top to the windshield by hand and then hit the cabriolet button to activate the latch motors, and that worked fine too…it went through the whole latching cycle and didn’t stop half way as it did before. So it looks like its working fine for now.

Thanks to all for your information and assistance. This place rocks!