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I've finally gotten round to writing up a guide on this job I did to my van recently - incidentally this is also my first post on this forum after lurking on it for some time! Hopefully it's of some help to anyone who's been thinking of giving this a go…

I recently added a central locking switch to the dashboard of my 2003 T5 - the main reason being I re-coded the vehicle to lock the doors automatically once you go over 5mph but quickly realised this is a real pain if you want to let someone into the vehicle without stopping the engine. It also seems like a real design miss that the button is only available in models with electric windows/mirrors despite still having central locking.

181510


I found this thread to be a very useful guide for doing this, however as the thread is a few years old now I thought I would post an updated version here going into more detail on how to install a suitable switch based on the little research I did. I'll reference upspex's guide a few times in this so probably worth reading it first if you are thinking of trying this install.

First of all, a few caveats:
  • This guide is for a T5, not 5.1 van. It may work on a 5.1, but in the other guide there are a few posts saying it was not possible
  • This is a locking workaround and does not use the official locking button circuitry, and works by mimicking a key in the door lock. I've read some warnings about this mode deadlocking the van (locking the doors from the inside) however I did not find this to be the case. The only behaviour quirk I noticed was that to unlock all doors you have to press the button twice (this could be fixed by re-coding the vehicle to unlock all doors on unlock signal)
  • This install does not require any vehicle coding, however to get the most out of it, it may be worth performing some of the changes I mentioned previously (auto lock/unlock, unlock all doors on unlock) via VCDS

In summary, what you are doing is:
  • Tapping in to the blue/yellow lock/unlock signal wire in the control module unit located behind the end panel of the driver's side dashboard (the piece of trim that can be pried off by hand when the driver's door is open
  • Connecting to a good earth point
  • Tapping in to a lighting illumination wire (if you want your switch backlit)

Upspex's guide talks about adding resistors to your switch in order to separate the lock/unlock signals, however I've found that as long as you use a VAG switch, this shouldn't be necessary as the resistors are built in (it also means you don't have to short any pins on the switch). The switch I used was from a Skoda Octavia, and cost £5 new off eBay. Whilst this switch will do the job, its worth noting a few niggles:

  • Lock and unlock are the wrong way round. I fixed this by carefully prying off the front of the switch, boring out the smaller of the two holes it clips on with (probably to prevent the front from being installed the wrong way round!) and reattaching it
  • The backlight illumination is Skoda green instead of VW red. Admittedly, this annoyed me much more than it should have - if you're really keen you could have a go at soldering a couple of red LEDs into the switch when you have the front plate off
  • The switch will fit neatly into the space left by one of the dashboard blanks, however you will need to fabricate something to cover the gap left above and below. I 3D printed a new part to solve this - more on that later.

Instead of ordering a wiring harness for the switch, I decided to keep costs down by soldering wires onto the pins directly. To do this, you first need to cut off the blue wiring harness connector housing, and bend the pins upward with a pair of pliers so they are easier to work at. The switch has 4 pins:

- Input
- Illumination
- Unused (for this job anyway)
- Ground

The easiest way to determine which way round your pins are is with a Ohmmeter and 12V source. First, connect the Ohmmeter to the outermost two pins and press alternating lock & unlock buttons on the switch. If setup correctly, you should see a differing resistance for each button. Now, connect a 12V source +ive to an inner pin, and -ive to an outer pin. The switch should light up. If nothing happens, try moving the +ive onto the other inner pin, or the -ive onto the other outer pin, until you find the correct orientation. Once you have everything working, note down your schematic and solder your wires accordingly. I made the connections in two parts to make it easier to remove the switch, but you could easily wire your loom directly to the switch if you want to save time.

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Image: locking switch from a Skoda Octavia. I wired all four pins initially but have since found you will only use three.

If you're taking care to follow the correct wiring colours, your connections should be as follows:

Input - Blue/Yellow
Illumination - Black/White
Ground - Black

To connect your switch, you will need to remove the dashboard end plate driver's side, and the lower trim panel immediately above the pedals. Feed your wiring loom through the dash blank you want to house the switch in (NOTE: the cutout pattern of the blanks means the left-hand side of the double blanks seems to work better) and track through until you can reach the wires from the opening at the side of the dash.

The Blue/Yellow wire is located near the bottom of a bank of connectors - the exact number will vary on the level of equipment in your van (refer to the original thread for discussion on this). For the illumination wire, I tapped in directly to the outlet of the sidelight switch. This was quite easy for me to reach as I had previously installed the auto headlight mod which extends the loom out from the back of the switch unit. For the ground, I just bolted a cable to part of the metal dash frame.

For the other connectors, I used spade connectors to tap into the wiring banks without having to cut any wires. This took a little trial and error to get a connector that was the best shape and size to be a snug fit.

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Image: feeding the wiring loom through the dash blank. I actually ended using the left hand blank here as the switch fits in snug

To finish the switch surround, I initially tried carving a hole in the original blank. My advice would be don't waste your time unless you are very patient. In the end I 3D printed a new part that served as a double blank, as the shape of the switch cover means it overhangs into the right-hand blank ever so slightly. The end result is quite a neat-fitting switch that doesn’t look too out of place, despite being strangely offset (and the wrong colour when lit up).

If anyone is thinking of giving this a go, I could potentially put together a kit containing all the required parts, or even just the switch and/or 3D printed housing. Just let me know in the comments if this would be of use to you.
 
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