4) Wiring the tailgate to the van.
By default, when the barn doors are unlocked, a pulse signal is sent from the BCM to the lock which tells an actuator to move some rods in to place; these connect with the handle, allowing the handle to mechanically pull on the latch and open the door. The same happens when the van is locked - this pulse moves the rod away from the handle, which is why you feel no resistance on the handle when you try it after having locked it.
The tailgate is, by default, wired so that the handle is always live. By this I mean that there is no lock or unlock pulse, but that the handle is in constant communication with the BCM - so that when the van is unlocked, no pulse is sent as the handle is waiting for your physical input - you squeeze the handle and the tailgate latch opens.
This is what makes the conversion a little trickier on the T5.1 and T6 vans - on the old T5 vans, the door handles were mechanical on both tailgate and barn door versions, so this pulse worked on both. When the electro soft-touch handle was introduced on the T5.1, this made the addition of either a timer-relay or wiring and coding a necessity.
As for joining the tailgate loom to the van loom, the rubber boot from the tailgate brings the loom in at the top nearside corner of the D-pillar to a 17-pin connector block. From there, a mating connector carries the wiring loom along the roof and down to the BCM (via a brown 10-pin connector at the nearside A-pillar);
the barn-door loom runs the same route from the BCM (via the same B-pillar connector), but the connector blocks (there are two - one for each door, shown as T17c & d on the
wiring diagrams) are in the D-pillar roughly behind the taillamps, the main one T17c being on the nearside.
NB: The offside connection T17d can be ignored, as this only powers the other half of the third brake light.
So, as you see, the barn-door loom runs past the point where the tailgate loom enters the van. This means you can choose to either de-pin your nearside D-pillar barn-door connector plug
or cut your wiring loom there and reconnect the cables to a 17-pin connector block that mates with that on the incoming tailgate loom (shown as T17o);
or you can make up a short (approx one metre length) loom with the corresponding male / female connector blocks on it (see below for part numbers) and connect the looms that way. The VIP section here has the wiring diagrams to show you the pinouts for these T17c / T17d / T17o plugs.
You’ll still need to run two cables back from this connection to the BCM if you want the wiring to work as if OEM
(
EDIT: see below for wiring and coding information).
The loom on the van is colour-coded whilst the tailgate loom wiring isn’t and can only be worked out from the T17o pinout.
NB: Ignore the numbers on the tailgate loom wiring as some seem to change once they reach the individual components.
Matt Vessey worked out the wiring on his Transporter tailgate conversion and utilised a relay to operate his handle, and now sells a relay with wiring and
instructions in kit form for tailgate conversions from his
Vagnostics webshop (along with gas struts).
A timer-relay will take the pulse signal and energise the relay so the handle can be powered for a period of time. However this was not a straightforward install on my T6 because it required me to have some basic electrical knowledge, which I didn't, so I opted for wiring to be added and coding to be undertaken to make the BCM work as though the van had a tailgate installed from the factory.
So if you don't have access to VCDS, have the Vagnostics kit and are not bothered about the timer only being energised for a short period of time, then this is the cheaper option that you can do yourself at home.
But if you want the tailgate handle to be energised all the time the van is unlocked, and the van to act like it had a tailgate fitted at the factory, then go for OEM wiring and VCDS coding.
The
Vagnostics wiring kit consists of a 6 pin relay that, when energised, is set to provide your actuator/solenoid with 15 seconds power when unlocked - this means that at all other times, the tailgate handle will effectively be switched off.
Relay wiring is as follows:
Pin 2 - wired to a 12v feed (wiring included).
Pin 5 - wired to a 12v feed (wiring included).
Pin 4 - joins the van loom at pin 14 (for the unlock pulse, which in turn energises the relay timer).
Pin 6 - earthed to van.
Pin 8 - joins the tailgate loom at pin 11 for the handle.
The relay interrupts pins 11 and 14, which should be earthed to prevent a loss in the electrical circuit throwing up errors in the BCM.
As you can see here, there lacks a provision for the numberplate lights.
Update: it appears Vagnostics is no longer in business according to others who have tried to contact him plus his website being down.
Alternatively you can opt for an OEM approach where the relay isn’t used and two cables are run from the tailgate to the BCM, with coding to accept the different locking requirement.
@Eddcameron of
VolksFit is the only outfit that I found able to do this (and I telephoned loads of auto-electricians but none knew how to tackle this).
Edd appears to know the VW electrical system very well and carries out all sorts of retrofits, both for private owners and for VW Listers Droitwich.
EDIT: DIYer and overall good egg
@Littleblackflash has managed to work out the wiring himself and has written an idiots guide
here.
In short, an ex-works tailgate-van has a
brown & yellow 1.5mm wire go from pin 14 the tailgate 17-pin connector block (4F0972483:4F0972575 - T17o) to pin 10 of the BCM-A 'J519' (black connector, right-side - T73a)
(via pin 5 of a brown 10-pin connector in the nearside A-pillar - T10ag) to operate the lock; and a
green 0.5mm wire run from pin 13 the tailgate 17-pin connector block (T17o) to pin 23 of the BCM-A 'J519'(T73a) (
via pin 4 T10ag) to operate the switch.
Pin 15 of the tailgate connector block needs earthing to the tail-lamp earth point on the D-Pillar.
Number-plate LEDs will be taken care of by the same feed.
A heated rear window will need a 2.5mm wire from pin 73 of the BCM-B 'J519'(white connector, left side - T73b) to pin 16 of T17o (via pin 16 of T17m - a red 17-pin connector in the A-pillar). I mention this as most people convert solid barn-doors to a glazed tailgate. The alternative is to have no HRW or to fit a Cali double-glazed window.
Coding can be found on the linked post.
Anyway. If you opt for the OEM wiring - which I would advise - then you absolutely
must click 'Like' on the linked post where
@Littleblackflash covers the
electrics and coding in more detail. If you don't, he'll drive round and cut your loom in half. And I'll luz a relay through your letterbox.
