overhead gauge install - dimmer wire?

[corprimo]

I'm installing dual temp and combo boost/egt gauges above the mirror on my '05. Anyone know which wire to the overhead module is for the dimable illumination? black/white is supposed to be ground, PK/DG is supposed to be fused ignition output, White/violet is listed as PCI bus, whatever that means, and red is listed as fused B(+), which sounds like constant 12 volt.



Thanks in advance!

 

[MLimpert]

I believe the dimming function of the overhead console is accomplished through the bus. If you move the dimmer switch from dim to bright rapidly, it takes longer for the display up there to brighten than the other lighting. This seems to prove that it is accomplished through the computer, and not a dedicated dimming circuit.

 

[corprimo]

Guess I'll just play it safe and tap into the orange/brown wire under the dash and run it up the A pillar along with everything else.