I saw this in the J-car section a few days ago and was going to pull the service manual and sorry I forgot. By interior lights, you mean the cluster illumination/VF display lights? Yes, full display brightness can be a real eye-burner at night. The dash illumination incandescent bulbs are grounded all the time and receive a varying '+' voltage from the BCM on an Or/Yl wire. The VF displays (PRND3L and odometer) receives '+' power all the time on a Rd/Vt wire to the cluster and the ground side of the bulbs are dimmed by the cluster circuitry itself depending on a bussed in request on the CCD bus by what the BCM sees from the desired dimmer control setting. Something may still be wrong with the dimmer control inside the headlamp switch. When the Parking or Headlamps are turned on, the 12 volts internally powers one side of the dimmer rheostat. The other side of the dimmer rheostat is grounded to the left cowl area sheetmetal and the variable wiper contact goes to the BCM on a Rd wire. It's like a voltage divider/variable resistor. By varying the control with the Parking lamps on, you should see voltage vary between ~2 to 12 volts if you can back-probe this Rd wire at the switch. If the dimmer has lost its ground and the wiper is staying at 12 volts, I would think that the illumination and VF displays would remain at full brightness whenever the exterior lights are turned on. I could not find any pinout or wiring diagram images on Google to help here and I know how much a picture can be worth a thousand words. Good Luck.
It is all good on the J section thing. You are quite busy on here as it is. Your information is yet again invaluable...
Yes, I mean the interior lights/VF display. My wiper has variable control still, so that means the ground is still good? I had to do a lot of re-soldering on the gauge cluster because the board lands for the tach and fuel gauge had received too much current over such a long period of time and had broken. The fuel light would come on and then drop the gauge to empty and then swing back to full repetitively when I had filled the tank. The tach would quit working all together. I only followed the lines on the tach and fuel gauge to fix this. But before the whole dash removal I did, the lights would flicker when I used my blinker. If I screwed something up on the gauge cluster, would just the gauges be bright and the rest of the car dim since you said they receive from the BCM on seperate wires?
I went out and checked and here is what I got;
Purple: Open Circuit
Red: Always Ground
Purple: Open, but dims VF display ONLY when lead is applied through meter continuity check to ground, .068 vDC
White: Battery Voltage (13.25 vDC) engine off
Red: Always Ground and also .018 vDC
There was no resistance from ground (rd) to body ground, so all appears good there if red is supposed to be ground. None of the values change when the switch is rotated. I am now confused.