Tailgate earth connection

[drinfinity]

To connect lights in my tailgate, I now have my feed, but I’m searching for the earth. I’ve reviewed the wiring diagram, and there are earth connections in there amongst all the cables.

Option 1: Pin 1 on the wiper motor connector is earth. But which of the four pins is pin 1?

Option 2: Earth connection 218 in wiring harness. Where is this physically before I start unwrapping all the neatly done loom tape?

 

[Pauly]

Just use the negative wire for any connection in there, if your only running light duty stuff you can tap into the numberplate light negative
As a general rule with VW wiring the negative is generally pin 1 on a plug but thats not a 100% rule, personally i would just turn the lights on and use a test meter to check voltage between each wire and (a good) point on the chassis

AFAIK Wiring loom connection points are not documented for exact location within the looms

 

[drinfinity]

Thanks @Pauly, I found the leftmost pin on the wiper motor (looking to back) was earth with a meter.

 

[bobbybasic]

Hey @Pauly I have a live cable in my tailgate from my leisure battery, I’d like to add some LEDs there, if I tap into a negative from the van wiring would that be ok, it can’t drain anything for the vehicle battery can it?

 

[rod_vw]

Standard German automotive wiring colours brown is chassis ground also numbered as 31 on items with circuit numbers. Anything else that tests as earth (-ve) is likely to be controlled by a module, BCM etc. and not always at that potential.

 

[bobbybasic]

Hi @rod_vw are you saying those (other than brown or numbered 31) that may test as negative may not be constant/permanently earthed?

 

[Pauly]

just use the negative for the numberplate lights and you should be fine

 

[rod_vw]

Hi @rod_vw are you saying those (other than brown or numbered 31) that may test as negative may not be constant/permanently earthed?

As @Pauly says, use the negative from the number plate lights.

However I was indicating that a brown wire in DIN standard automotive wiring is a true chassis negative or ground which ever term you prefer. There are a number of items in Volkswagens that are negative switched i.e. a module controls the negative connection the most notable circuit being the control of interior lights.

Us Brits tend to think of brown being the live wire as in domestic 220v circuits and this does cause much confusion with electricians who predominately work on UK domestic wiring. Don't delve into the colour codes via Google as it will throw up more questions than answers. If you want to look into VW wiring access the genuine wiring diagrams either vis VW's own portal or cardiagn.com and VW workshop manuals.

 

[Littleblackflash]

To make things more fun, VW only use white cables in the tailgate harness, but they do laser mark each wire.

The best earth to use is the one from the heated window. Its a separate earth to all the other functions and is a 2mm wire. It's unlikely you'll have the heated screen on and the lights on for a long period.

 

[bobbybasic]

just use the negative for the numberplate lights and you should be fine

Excellent. I've just got back from the van having done exactly that!

 

[bobbybasic]

To make things more fun, VW only use white cables in the tailgate harness, but they do laser mark each wire.

The best earth to use is the one from the heated window. Its a separate earth to all the other functions and is a 2mm wire. It's unlikely you'll have the heated screen on and the lights on for a long period.

This makes sense, thanks.