For those with interior lighting problems where you turn on the headlights and the dash goes dark, I'm attempting to find the solution to the problem. I'm very close and have isolated it down to one discrete electronic component inside the lighting module. I'm in the process of finding a suitable replacement. Stay tuned for more. I'll try to post pics too.

 

That would most likely be a problem with the dimmer potentiometer on the LH pod, which controls the incandescent cluster illumination and flourescent tube brightness through the light control module, which is located under the passenger side dash. You may want to try contact cleaner to remove debris from the resistive surface on the pod PC board that the pot wiper contacts, and make sure that the PC board is secured to the pod front panel, as the pot wiper to PC board contact pressure relies on the board being securly fastened to the pod front panel.

 

Tim,

Already done. Checked resistance too - nice, smooth ramp from 4.8 ohms up to about "I can't remember" kilohms.

It's definitely the light module.