Tips for Wiring a 2009 Volkswagen Jetta Wolfsburg Edition with a 4-Way Trailer Wiring Harness

Question:

I’m having a heck of a time wiring my 09 VW Jetta. Wolfsburg Edition All is great till I turn on the head lights. I then watch the video for wiring harness on a 2008 Jetta and he said to combine the red wire with the white ground wire. I’m not sure what is going on. Do I ground the brake wire or not? The hidden hitch I ordered from you a couple of weeks ago installed just fine and looks nice. Then I have to install your Optronics Waterproof LED Trailer Light KitTLL6RK and I’m sure I’ll be back asking questions about that. Thanks’ for any help you can give.

asked by: Gordon F

Expert Reply:

What it seems to boil down to is if the vehicle has a 2 wire system or a 3 wire system. On a 2 wire system, you would ground the red wire with the white wire. This is because the stop and turn signal lights are combined on one circuit.

On a 3 wire system, the turn signals are separate from the stop light so the wire needs to be connected to the dedicated brake light wire.

What it sounds like is that the running light brown wire is getting connected to the wrong wire on the vehicle. VW wiring can be tricky and finding the correct wire may not be easy. It is possible that more than one wire will have more than one function, the trick is to determine what the main function of each wire is using a circuit tester like # PTW2993.

If you turn on the headlights and then test each of the wires, you may find more than one carrying a signal. However, the test light may be brighter on one of the wires and/or that wire may not show a signal when the brake is pressed or turn signal engaged. In that case, you know you have found the running light circuit.

expert reply by: Michael H