2014-06-08 born_slippy found the same wires in the battery compartment so one doesn’t have to open up the trunk trim to do this.
Yellow/WhiteGreen/White wire from convenient module is the same wire as trigger/green wire at the latch.
convenient module plug
Yellow/Green wire from motor plug is the same as the switch button (GREEN) and brown is any brown wire as ground
We have 2 cars that have motorized trunk lid, we want to close the trunk lid with the door button or the remote since they’re not options on both of our Q7 and A8L. We tried with the A8L first and it seems to work well.
According to my findings:
1. When we push the door switch or the remote to close or open the trunk, the latch wires (3 pins: Green, Brown and White/Black), Green and Brown pulses 12V between them – this will be the trigger for our relay coil.
2. When the trunk is opened, the close switch (black rectangular button on top of the trunk lid) with 4 pins: White/Red, Green, Brown, Brown: White/Red will be 12V and 0V when the latch is in the close position. When we push the button, the 2 center pins = Green and Brown will short to each other as long as the button is pushed.
All we need is a relay that triggers at 10-14v. The trigger input positive should be connected to the Green wire on the trunk latch. The negative should be connected to the brown wire – leave the black/white wire alone.
The outputs of the relay(open then short when activated) should be connected to pins 2 and 3 (center 2 pins) of the close switch.
That’s it.
When you buy a relay – the coil will have pin # and sign + and -, the positive (+) pin of this coil goes to Green and negative (-) pin goes to Brown.
The relay PIN B and A go to 2 center pins of the switch (Pin 2 & 3) doesn’t matter which color because A will short to B when the coil is activated (the first relay picture – SPST).
11 Comments
Hi, I have been trying to get this to work all weekend on my 2013 UK Q7.
I know I am missing something but cannot work out exactly what so I am throwing myself open to any advice.
On the Q7 the latch trigger is a white/blue and the close button in the trunk lid has a blue/yellow and brown wires which when joined close the lid.
When wired as per your advice it’s a no go. If I power the relay from a supplementary 12v source (12v socket in boot is handy) it triggers the closure. Likewise, if I trigger the relay from the latch via remote and replace the wires that go to the closure button with a 12v lamp it lights the lamp so from this I have ascertained that the latch can power the relay and if the relay is manually triggered by means of 12v it will short the outputs and close the lid.
I have even used transistors to let the latch trigger allow 12v picked up from the boot light to trigger the relay in case it was a current draw problem. I have also used a capacitor to keep the relay open for 1 second.
What I have noticed is that the boot closure activates when the blue/yellow and brown in the close button is joined and released not when it is joined.
I did open the latch the other day and I tested everything out, it was different from A8 trunk, although the latch switch operates the same – I tested with an Ohm meter. The Trigger pulse is the one we need to find out. I haven’t had time to do it. Can you show me the pictures of how to remove the liftgate cover completely out? I was afraid to break something. I only removed the 2-3 front clips, barely to lift the cover up.
No worries. I started to photograph my attempt in case I got it to work so I could share my findings like you did.
I’ll take a photo of the back of the card to show you where the clips are as well.
The part I had trouble with was where the trim that surrounds the window attaches to the card. I managed to bend the plastic pins but they went back into shape ok.
It’s dark here at the moment (9.30 pm) so I’ll grab a few photos in the morning b4 work and post a link to them in case it helps.
A thought that has been playing on my mind was that maybe the system will not allow a close signal to be recognized if the latch is receiving the open signal so today I shall be playing with a couple of 555 timer chips to see if I can delay sending the close trigger by 1 second after the latch gets the open signal.
I’ll let you know. Damn this time difference!
I haven’t tested the pulse of the connector at the latch – if you connect the trigger side to this latch connector and the output to the close switch, it may work.
OK, I’ve got it kind of working.
What I mean is that my theory was correct; the trunk closure button has no effect when pushed while the latch is getting the release pulse so powering the relay from the latch release pulse like you did on your A8 does not work.
To counter this I used a pair of 555 timer ICs to insert a one second delay from the latch getting the release pulse (when either the remote button is pressed or the trunk release button on the door is pressed) to trigger a relay that starts the 1 second count and then fires another relay which triggers the trunk close by shorting the two center wires in the closure button (brown and blue/yellow) Also, since the brown is just an earth the blue/yellow can just be shorted to earth to save a wire.
Now the problem – I have powered the circuit from the lamp situated in the trunk lid that comes on as the trunk opens. I did this so that the circuit was not powered up all of the time but this is where the issue occurs: the circuit, when first powered up, runs through the cycle and… you’ve guessed it, sends the close signal one second after the damn trunk light comes on, which happens to be as the trunk is half open!
I am toying with the idea of changing resistor/capacitor values to set the timer longer (Ithink about two seconds will do it) but the fear is if it sends the pulse after the trunk has reached full open it may just close it again straight away.
I have pictures of various parts of the lid which hopefully are high resolution enough to see the clips etc on my dropbox here: https://www.dropbox.com/sh/1ygzngri2nz9xtd/AACBoxJmG-tzeACyxMxe11nca