So, none of my center column lights are working, none of the switches, none of the A/c Control and none of the window switches (the shifter light itself is working) Also the ashtray light is working. Fuse seems fines. I have replaced the bulbs in the center with known tested good ones. Just can't seem to get any power. Could this be a rheostat issue? The dash lights work but do not dim up or down. What's would be a good next step?.

Oh, this is on the 85 300TD.

The bulb that feeds the fiber optic "spider" is probably burned out. The rheostat is another issue.

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'83 300D, 126K miles.

No, I've replaced that bulb, along with all the bulbs for the A/c control. I have no power to that entire strand of lights and no power to the lights of the window switches. or any of the other switches around the shifter....

Everything else seems to work, all entry lights etc. and the dash itself( as mentioned before)