C2 cabrio roof issues

[YPVS]

I adjusted mine in the gear and I definitely got farther along. Make sure you check the switch on the windshield part too. Now I need to see what you mean about the clamshell switch in the back.

It's not the clamshell POT which determines roof position, it's a POT on the left hand hydraulic RAM. To get to it, you really need to take off the rear interior panel to the left of the rear seats.

The position of this POT is moved by an arm and a pin on the ram, so as the ram moves, the POT turns and the voltage changes.

PIWIS can show current voltage of both this POT (and the clamshell POT). You can move the roof to various stages of opening 1-6 and see if the current voltage falls within the appropriate of the 6 saved calibration values, which might range from 0.8V to 3.5V or similar. One of DeMort's documents on here shows the 6 positions of the calibration values.

 

[dcapper]

My pot 2 1-4 are all reading the proper values in my PIWIS. But I'll look at removing that panel and taking a closer look.

 

[YPVS]

My pot 2 1-4 are all reading the proper values in my PIWIS. But I'll look at removing that panel and taking a closer look.

POT2 1-4 is the clamshell. POT1 1-6 is the top.

I think we're at a similar point. My POT's are displaying voltages pretty much in the range for the calibrated values 1-6 for POT1 (roof) and 1-4 POT2 (shell lid).

I can raise my roof perfectly from half way and can lower it to half way (the stop point is when POT1 and POT2 reaches 2.51V. After this I need to raise it a little bit by opening the bleed valve and raising a bit before tightening it back up. It will then raise and lock as normal and the clamshell comes back down and locks as it should.

The fork you mention on the roof latch, does the same to me. When hanging free and pushed down by the spring (down) PIWIS sees the roof as "Convertible Top Raised". It does this even if I fully lower the roof by letting the pressure out of the pump. If I then pull the top up to half way, it works on the button, but as soon as this fork hits the top of the windscreen and is pushed up into the latch, PIWIS immediately shows "Convertible Top Not Raised". It then latches up as it should, all windows rise as they should and all values in PIWIS look correct.

My POTS are reading correctly, the shell and roof can operate correctly in both directions, but stops when the POTS go higher than 2.51V even though the POT values are in the calibration ranges with the roof and clamshell in all positions.

The fork on the roof appears to be reading the opposite of what you'd expect. I'm going to Google the fork issue and re-read DeMort's docs as now I understand more, something may make more sense.

 

[dcapper]

Wow! You and I are at the same point. I'm going to re-read the two pdf's I have and see if there is something we are missing.

 

[dcapper]

How do I release pressure in the pump?

 

[YPVS]

How do I release pressure in the pump?

There's a little Allen screw on the ally plate, on the right hand side of the front facing edge of the pump. This is a little bit to the left of where the clamshell screw would be.

Just loosen it half a turn or so and you'll be able to lift or lower the roof manually. Just nip it back up then. It's standard thread. Anti clock to loosen.

Mine didn't seem to lose any fluid at all over the many times I've done this to move the roof about, once it stops at half way down.

 

[dcapper]

Got this from a member on Rennlist:

Don't believe the finger switch is the issue or pump pressure .There is a top position sensor 996 613 31302 that may not be reading correctly .I know nothing about piwis but it might be one of the sensors that can be recalibrated .

 

[dcapper]

Wow did I get far tonight. I did see the pot arm for the roof in the side panel but it looks like it's working. Have to figure out how to calibrate it. So when I hit the close button on my dash. The latching hook locks, the clam shell closes, and the windows roll up. When I hit open, the windows roll down, the clam shell opens up, and I hear the pump but that's about it. The roof doesn't move. Obviously back to the pot readings being backwards. So here is my readings.

Pot 1 - 1.04 V
Pot 2 - 1.25 V
Calibration Pot 1 Value 1 - .94 V
Calibration Pot 1 Value 2 - 1.45 V
Calibration Pot 1 Value 3 - 2.10 V
Calibration Pot 1 Value 4 - 2.55 V
Calibration Pot 1 Value 5 - 3.25 V
Calibration Pot 1 Value 6 - 3.53 V
Calibration Pot 2 Value 1 - 1.59 V
Calibration Pot 2 Value 2 - 1.88 V
Calibration Pot 1 Value 3 - 2.06 V
Calibration Pot 1 Valve 4 - 2.78 V

 

[YPVS]

Wow did I get far tonight. I did see the pot arm for the roof in the side panel but it looks like it's working. Have to figure out how to calibrate it. So when I hit the close button on my dash. The latching hook locks, the clam shell closes, and the windows roll up. When I hit open, the windows roll down, the clam shell opens up, and I hear the pump but that's about it. The roof doesn't move. Obviously back to the pot readings being backwards. So here is my readings.

Pot 1 - 1.04 V
Pot 2 - 1.25 V
Calibration Pot 1 Value 1 - .94 V
Calibration Pot 1 Value 2 - 1.45 V
Calibration Pot 1 Value 3 - 2.10 V
Calibration Pot 1 Value 4 - 2.55 V
Calibration Pot 1 Value 5 - 3.25 V
Calibration Pot 1 Value 6 - 3.53 V
Calibration Pot 2 Value 1 - 1.59 V
Calibration Pot 2 Value 2 - 1.88 V
Calibration Pot 1 Value 3 - 2.06 V
Calibration Pot 1 Valve 4 - 2.78 V

Your POT values are pretty much the same as mine, give or take .05V.
The current readings of 1.04v and 1.25v also look correct for the roof to be up and locked (POT 1 value range) and the clamshell down and locked (POT2 value 1 range).

If you move the roof and clamshell to a different position, you should see the POT voltages go up, moving it into the corresponding 1-6 or 1-4 calibrated range. Those values as far as I understand, are the last calibrated values of the POT's.

 

[YPVS]

Got this from a member on Rennlist:

Don't believe the finger switch is the issue or pump pressure .There is a top position sensor 996 613 31302 that may not be reading correctly .I know nothing about piwis but it might be one of the sensors that can be recalibrated .

That part is just the POT on the hydraulic RAM - POT1
The voltage from this lets the control unit know where the roof is as the voltage value should go up and down the 1-6 POT values as the roof is moved from fully stowed open to fully closed and latched.

https://www.deroure.com/diagrams.asp?MAK=3&MDL=25&TBL=2673&SMA=0&SMO=0&ST=99661331302&SC=1

 

[YPVS]

This looks very interesting for both of us.

When the roof stops halfway during going down, the position it stops at is meant to show which microswitch has missed it's signal.

Most seem to be in the latch mechanism.

https://www.renntech.org/topic/44431-996-convertible-top-1999-cabriolet/

Mine stops at 2.51V POT1 value on opening, putting it on mine, just into POT1 Value 4 - "Convertible top at middle/rear". This looks like the 3rd example down for me and the Microswitch next to the rear of the motor in the latching mechanism.

The fork on my latch definitely is back to front in PIWIS, although it does seem to latch and unlatch properly. I'm going to have a crack at removing the latch and checking the obvious this weekend.

 

[YPVS]

Slow progress. Rain stopped play.

It made no difference taping the plastic fork on the latch (which appears to be reading backwards in PIWIS, i.e. "Top Not Raised" when it meets the windshield and is activated, then "Top Raised" when it's fully down).

I also noticed that the actual value for "Speed" in PIWIS measures "Speed > 5KM/H (3MPH)", which is odd when I'm on the drive, parked up. Apparently greater than 3MPH will stop the top working.

I'm beginning to wonder if this Chinese clone is reading a few things back to front. Googling results from others shows people reading > 5km/h though.

I'd love to test the flaps again, but from PIWIS any action you try to take withy the roof lower than POT Position 4, half way down, is met with a quick click of the control unit then "Function Inactive - End Position Not Reached".

The frustrating thing is, the roof will raise and lower perfectly up and over half way up, including the clamshell opening and lowering/locking, so clearly the bulk of it is working.

I'm going to have to find a way of trying the flaps again. The sensors seem to read them down and not up OK, but maybe they need to start raising when the roof hits level 4 of 6 in closing and when the flaps lowered microswitch is still telling it they're down and not moving?

Weather permitting, I'll look at the latch mechanism tomorrow, but that all unlocks and locks fine, using the button. The only issue being PIWIS reading the plastic fork on the latch, which tells it it's hit the windscreen, is seemingly reading backwards.

 

[dcapper]

You're way farther than I am. I can't get the roof to move at all.

 

[YPVS]

You're way farther than I am. I can't get the roof to move at all.

Is it locked shut or open? If open, you might need to do the manual clamshell open thing but this tends to need the repair kit fitting, which is £50 for the early cars. Handy though, because you can use the old, twisted shaft to manually turn the clamshell gearbox with a set of mole grips.

If it unlocks but doesn't move, do you hear the pump try? When mine refuses to move as it gets to level 4, all I get is clicks from relays.

 

[YPVS]

Well finally! :mrgreen:

After weeks of learning the ins and outs of the 996 cabriolet top system, I finally got to the bottom of it.

I reset the latch as per the dot line up procedure, as my cogs were one tooth out. This didn't fix it. Double checked the flaps with a battery and both worked fine.

In the end, I noticed in PIWIS that the POT2 (clamshell POT) voltage got to 2.51V and never increased from there. This was with the shell fully open and up,. Now, I had set the resistance to 6.2Kohms at end point (which I assume is fully up) as per the instructions, which got it there or there about in PIWIS apart from the upper level.

My PIWIS calibration value was 2.75v at position 4 of 4, fully up, yet the real reading was only 2.51V. I took the POT off and tweaked it until it hit 2.9V (as it must be above 1v at lower limit and under 3v at upper limit). Put it back together and BOOM! The top lowers and raises as it should.

Just got to tidy up the headlining and put all the trim back now.

Still wont calibrate with PIWIS, but I'm beginning to wonder if these Chinese clones aren't 100%, what with backwards readings of the roof up sensor on the latch.

Anyhow, I've learnt an awful lot about how these work, so thanks for the input from DeMort and others, without the knowledge, links and documentation, most of this would have been impossible! :thumb: