Car has been sat for a couple of months, outside during british winter (i know )

Roof now won't open past halfway, with a fault light displaying on the dash. I have visually inspected everything and cant see any stray cables, worn or pinched strings/fabric, no obviously broken parts. It will close from the half-way point just fine.

The fault code is:

Address 26: Auto Roof Labels: 3W7-959-255.clb
Part No: 3W7 959 255
Component: VSG BY615 0509
Revision: 00005000 Serial number: 00000007583180
Shop #: WSC 00158 106 71023
VCID: 0407B5E04482D56AF1-515B

1 Fault Found:
02000 - Switch Position
008 - Implausible Signal

A look around Google suggest this is most likely a sensor/microswitch issue where the car decides it's not safe to continue opening the roof because it cant explain the readings its getting (for example it thinks the windows are still closed, or the tonneau cover still closed).

Only microswitch I could find was the one that checks if the tonneau cover is open or not. Tested it and it seems to work fine so i'm moving that down the list.

Any ideas where to look next?

 

Has it been on a battery tender that whole time? Make sure both batteries are golden first.

 

Yes, Optimate.

 

You are on the right track the hood mechanism is a off the self unit used in many vehicles , merc s etc .Its just the shape and cosmetics that are different the gubbins and control mechanisms are the same .
Guess webasto ? ( I have a coupe ) .
There will be micro switches all over the place and I know the ECU is under the drivers seat .
When I take my car to the Indy they always have a few GTC s in with faulty micro switches ...,water ingress .
The rear side panels ( where the windows sink ) and the front seats are removed .....it’s pretty labour intensive .

This is over and above the support hoops becoming loose and misaligned from stitch failure that’s a Bentley only issue .

This micro switch “ implausible “ signal is a broken wire or short to ground from damp .

Double check there’s no damp got into the under seat ECU s as well from leaky roof and resultant damp carpet .

As for leaving it out side ........can’t think of another car that has so many potential issues from water ingress leading to electrical gremlins .

There's plenty that need over 13.2 V to not throw a CEL .....but are ok parked outside in U.K. weather .....trickle charger is only 1/2 of the must do with one of these .
.

 

Thanks, I’ll remove some trim and look for
damp. I wasn’t aware the roof module
was under the drivers seat though?

I found on IETIS that there is also a variable potentiometer somewhere, which I hadn’t seen or tested. I think I’ll remove and test the first, then try manually opening the roof just to confirm no physical issue.

 

Hello John,
I think you may have some confusion, the "ECU" AKA ( Engine Control Unit ) is not under the drivers seat, they, as there are 2, are located under the bonnet at the firewall.

The module under each front seat is just for that, each front seat, they are the seat control modules, under the carpet on the drivers side (USA) is the KESSY control module for the security/IMMO system, and a box with 4 circuit breakers, 1 for the left side window lifts, 1 for the right side window lifts, 1 for the driver's seat control module, and 1 for the passenger seat control module, under the carpet on the passengers side at where the carpet curves up to the firewall is the body control module, and some relays.

Now as far as the roof control module, it appears to be on the hydraulic pump itself, along with 2 relays for the roof system, see #4 in the diagram and link.

https://www.scuderiacarparts.com/par...124/2129/38522


...

 

I was using E as electronic .
Its just my guy seems to always remove the front seats ( UK RHD ) when doing GTC hood micro switch jobs .
Maybe it’s just to gain better access ? Or linked ? .
Tells me water ingress is the culprit.

 

SOLVED - Investigated further today. The potentiometer (in the picture in my previous post) Was sticking, so wasn't returning to its home position. Pushed it back with my finger and the roof then opened fully without issue. Closed the roof and the fault light on the dash went away.

Repeated the same process 3/4 times and worked as expected each time.

Next step is to remove the potentiometer and give it a good clean with contact cleaner. If that doesn't work then i'll try to source a replacement.

 

Excellent thread with a good solution, thanks for sharing your experience

 

Great problem solving! Glad to see you figured it out.