Carista is a mobile app that lets you customize your car for your liking, check it for problems and clear any fault codes. All you need is the Carista app (available both for Android and iOS) and an OBD2 adapter.

One of the very cool customizations that can be enabled with Carista is turnning on the lightning of the gauge needles and scales even when headlights are off!

This is how you do it:
You need to plug in your OBD adapter, open the Carista app on Android or iOS, click “CUSTOMIZE”, then go to “Instruments / Display / Dings” and set both of the following settings to YES:

• Gauge needles lit even when headlights are off
• Gauge scales lit even when headlights are off

After you have done this, both the needle and scales will be lit regardless of your headlights, as long as it is daytime (or the sensors of your car detect enough light to consider it daytime). However, once the car decides it is time for headlights, it will turn off the scales lighting in order to remind you to turn on your headlights and there is no way to change this behavior. Hence you should try the customization at bright daylight.

This also works on Audi A4, S4, RS4, A5, S5, RS5 (all B8 platform); S6, RS6, A7, S7, RS7 (all C7 platform); A8, S8 (all D4 platform) and Q5 models.

Here you can see sample list of customizations available for the A6: Customizations | Carista OBD2 - Vehicle Diagnostics and Customization