Electrical Engineers - How to dim interior LEDs?

[Bromie]

I have a technical question for the Volvo electrical experts out there.

I've recently upgraded my 2016 XC60's gear knob from the boring standard leather ball to the V40 illuminated gear knob (the holographic one) as I thought it was the one thing holding the interior back. Everything has gone well, however I'm trying to decrease the brightness of the gearknob as it looks a little 'garish' at night.

I've trawled through the electrical diagrams for the XC60 and V40 but as far as I can tell, as the gearknob was originally designed for a different car, the car's CEM just isn't designed to properly control the brightness as it would in the V40. I have tapped into the handbrake switch LED as I knew it dimmed with the dashboard lights, however I could do with some help understanding its behaviour.

The dashboard dimmer will reduce the brightness of the gearknob up to about a 1/5 of a turn from maximum, but below that level the LEDs just go off. As a second attempt I've tried using an off-the-shelf PWM dimmer, however this has the same behaviour.

I can only assume that there is some circuitry inside the gearknob circuit board that will only work with the V40's CEM, but I'm hoping someone has a suggestion for a workaround.

Is anyone able to explain how the system works? Or can anyone think of anything else to try which may work? I want to try and stay away from soldering resistors, etc., but if that's the only option then obviously I'll consider it.

Many thanks, Dan.