987 Instrument illumination?

[JW1]

Hi All,
It will be great if someone can advise me on how to increase the brightness on my instrument dials on a 3.4 987. I am familiar with the adjustment button on the dash which when turned only indicates to me that the lighting is dim and I don't seem able to make it bright, as in the knob/button only turns one way. Is there a special method required to make the light brighter?
James.

[Zyp]

It should turn both ways, and then an icon saying 'dimming' should appear in OBC window.

[SFO]

I think there a 2 knobs, one near the clock, the other, the tacho ..

tacho knob controls the dimming

[JW1]

Thanks for your replies, the knob on my car only apppears to turn one way. I will take another look.