# 'Bootlatch servo Mechanical failure ' led up the garden path!



## Dangerrous (Sep 14, 2014)

Okay, so since replacing the troublesome amp on the Phaeton the auto boot function hasn't worked.

Before changing the amp I disconnected the accessory battery just incase of any problems. Reinstalled, the new amp burst into life BUT the auto boot function stopped working. So I connected up my vcds, only to find that my vag com cable had become faulty, a few weeks later a new cable and some tinkering in module 46 led to a repeated dtc

Sunday,22,March,2015,12:11:25:62939
VCDS Version: Release 12.12.0

Address 46: Central Conv. Labels: 3D0-959-933.lbl
Control Module Part Number: 3D0 959 933 F
Component and/or Version: HSG 0101
Software Coding: 0000040
Work Shop Code: WSC 00417 210 81010
Additional Info: 3D2959701E Tuersteuergeraet FS 0104 3D2959702E Tuersteuergeraet BF 0104 3D0959703E Tuersteuergeraet HL 0201 3D0959704E Tuersteuergeraet HR 0201 
Additional Info: 3D0909610C 3L HDSG 2330 7L0907719 Neigungssensor 0020 
VCID: 3365F94751C0B386591-4A9C
2 Faults Found:

01699 - Motor for Central Locking; Hatch/Trunk (V53) 
003 - Mechanical Failure - Intermittent
00896 - Trunk Lock Unit (F256) 
008 - Implausible Signal - Intermittent

#This was the last reading I took with the repaired boot latch servo reconnected#

So first job was to remove the boot trimmings so I could get to the lock



Then I had to take the plunge and separate the servo mechanism, there are two pressed rivets that perform two functions, 1) stop people like me reparing an expensive unit and 2) hold the metal casing together on the catch pivot point. I drilled out the top of the rivet head and then undid the torx bolts




The original vcds readout was 'boot latch mechanical failure'
I had tracked down two bootlatch servos, one in Poland and the other in Germany, so I was prepared just incase I messed my one up, or it was broken beyond repair.

The original fault was that the finger which allows the latch to retract in it's housing had ridden over the hook and wedged itself against the micro switch, the screwdriver is pointing to the microswitch, the finger is the one to the right and the hook is under the top finger



I took the unit apart and investigated why it had happened, it seems if the motor is overdriven there's enough play in the mechanism that the finger can jump the hook and wedge itself in the gap!

Here's a photo of the servo with all its workings exposed, the latch has three separate layers performing different integrated tasks, each sprocket has to be positioned at a specific angle to drive the two fingers and latch correctly.




Next I spent a good couple of hours getting the mechanism working as it should mechanically, then I re-attached the motor and fitted it to the car. I thought that would be the end of my problems, but no. The vcds kept on picking up the same fault, so I stripped the unit back down and checked it again, also belling out the micro switches. All was as it should have been

So next step of frustration was to check the communication to module 46 
Measure blocks around 24-28 let me see the micro switch feed to the module, ALL OKAY:banghead:

Next I checked the motor, giving it a direct feed- strong as an ox 

I then trundled around the forum and noticed a picture showing the broken clips from the trim surround of the boot harness ball joint (same as mine), and read that the power supply to the motor has to be sufficient or it brings up a motor fault
So like many other P owners I stripped down the boot wireloom and look what I found




It seems that the car has suffered the typical wire feed fault and has been previously repaired. My job next weekend is:
Saturday- test and where necessary repair the wire loom (previous repair was very neat and will help me sort it for good)
Sunday- carry out an interim atf change using Lifeguard6 for confirmation of old atf related problems

I'll report on my findings next week, hope it's got a good outcome
Darren


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## Dangerrous (Sep 14, 2014)

*Start of this weekends jobs*

So already armed with the knowledge that the Phaeton boot harness is a common problem and that mine had been repaired once before. I started the second repair to this area.

I removed the rain gutter, and the ecu carriage trim. This is where I could see the extent of the repair, it seems the car had indeed had the 'half loom' replacement. Part of the join can be seen in the photo below, look to the right and you can just see the insulated crimps




The original wiring loom had just been left dangling



I opened up the loom and just pulled the cut lengths out, simples.



The broken wire that caused the original fault is shown here, no surprise here



Next I had to raid the A8 for appropriate wire and then start to make up a new harness, I was very careful when threading it through the tube, Loads of talc and patience finally paid off and all the wires were through


Taking note of the warning by Micheal with regard to 'same colour' wiring in the harness I joined each one up and tested- all good




Lastly I connected the modules back up, carried out an adaption, and ran the boot through the motions via vcds- all good

Finally I've got my auto boot back
I've got some Tessa tape coming in a few days, I'll tidy the wiring up once it's wrapped up, I still need to take the servo off to weld the rivets back up.
Darren


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## n968412L (Apr 23, 2009)

Nice Job Darren:thumbup:


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## PizzaSoft (Dec 3, 2012)

I'm sorry to clutter the nice post here but I went through the repair/replacement of the lid loom and I messed it up badly.
It all ended up in tears when the boot latch mechanism exploded under its own power and spat plastic bits of the spur gears inside.
I have narrowed down the issue to a swap of the end stop switch wires as per images above of the open unit.

Now when I had to open the unit to admire over the aftermath of my work I have access to all four switches and I can tell that they all produce reaction in advanced measurement values in "46-Central Conv." module but I have no way of saying where I went wrong as this boot lid loom has been mended prior to me reattempting it. I always had the lid behaving oddly since I acquired the vehicle.

Can anyone who has got fully operational assisted boot and a VCDS program to make me three snapshots and post them to me of these four parameters when his lid is fully open, fully closed and just unlocked with the key from the barrel in the boot lid?

F256 Lock,detent pawl
F256 prong,catch bolt
F256 lock,detent
F256 detent,swung in

If there are any schematics of the wiring between J605 and F256 and a word where to find J605 that would also help enormously.

Thank you very much

P.S.
Obviously I'm looking for a replacement F256 boot latch unit in good condition priced reasonably.
Please PM me.


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## Dangerrous (Sep 14, 2014)

http://allegro.pl/zamek-tylnej-klapy-vw-phaeton-dociag-3d5827501h-i5450443770.html
this is just an example from our Polish friends

works out £52 plus shipping (and a lot of hassle if you haven't done Allegro before)

Alternatively look on ebay.com I had one come up at £100 plus shipping from Germany, when I was originally looking

The controller is under the rear tray as in my earlier post, they are readily available if needed.

Most bootlatch problems seem to stem from the wiring loom. This is a long tedious job, patience is required.
Darren


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## curiousnewguy (Aug 7, 2016)

I have taken apart my latch to check if its all right inside of it just to realise that i have no clue of how it is supposed to look 

In the picture where the latch is open to see its isnides. Is it set the way its supposed to look or is this how a "broken" one looks?


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## Dangerrous (Sep 14, 2014)

my latch was never broken, but you can see how it all works by twisting the motor drive round.
D
That is how it's supposed to look


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## najel (Apr 10, 2008)

My latch seems to have this exact issue. It seems to me than that the original fault in the latch is caused by the broken wires? A signal that should tell the controller to stop the motor does not reach the controller, and then forces the latch mechanism to move further than it should. 

I have not found the broken wires yet, but I did get a full replacement harness from the person I bought my car from. I will disassemble the latch serve mechanism to see if mine suffered the same failure as yours, but I'm quite sure it has. I will also splice the entire new harness. My current one must have had some work done before, I don't see any splices, but the box that allows the slack to slide in and out is completely removed, there was just a loop of harness under the trunk lid trim.

Anyway, I realize this is really old and you're probably no longer here, but wanted to say thank you for posting those pictures 5 years ago!


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