In this guide we’ll show you how to connect the dimmer wire on a MK7 Golf. For this demonstration we have P3 Cars OBD Vent Gauge that needs to be wired up accordingly.

Difficulty Rating


Tools/Parts Required

  • Trim Removal Tools

Step 1

Using a trim removal tool, pop off the side trim to reveal the wiring.

Step 2

Remove the switch assembly. To do so, push the dial inwards and turn to the right.

Step 3

You can now pull the switch assembly out from the dashboard.

Step 4

Press down on the red tab to release the connector and place the switch assembly to the side.

Step 5

Prepare the GREEN dimmer wire for your gauge and the GREY factory loom wire. This GREY wire will provide the switching current.

Step 6

We will be using a 22-18 AWG wire tap to intercept the GREY light switch wire.

Step 7

Connect the wire tap to the GREY and GREEN wires, then squeeze with pliers to terminate the connection.

Step 8

As you can see, the metal terminal has wrapped around the factory wire, providing a perfect connection without completely cutting the wire.

Step 9

Close the wire tap cover and use electrical tape to neaten the installation.

Step 10

Pull the loom back into the dashboard and reconnect to the switch assembly.

Reinstall the switch assembly by pushing it back into the dashboard and rotating the dial to the ‘OFF’ position.

Step 11

Reinstall the side trim cover.

Step 12

Test functionality by switching the headlights on and off. Your gauge should dim when the headlights are turned on.

For those using a P3 Gauge, be sure to enter the settings menu and change the display options to ‘On.A’.

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This Post Has 3 Comments

  1. Justin

    I have a mk7 GTI, is there a way to hook up the green wire to the actual dimmer switch to control the brightness in conjunction with instrument panel lights?

    1. Staff @ AutoInstruct

      I believe it depends on your gauge. Some only have a high/low brightness level, and not variable like your cluster.

      1. Justin2

        I asked the same question to the P3 guys, and they told me “no”, the P3 gauge for the mk7 GTI only has the two brightness levels.

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