First as always is fuses, either replace them or clean the contacts. Replacing with the porcelain copper fuses is best, the plastic ones will melt and lose contact in moderate resistance situations


Then fiddle with the rheostat. It's the left knob on the cluster that controls brightness. They lose contact over time and lack of actuation. I had to install a jump wire in my 83 sd. It's always at max brightness which is still too dim for my taste.

After that, pull the radio, then turn the lights on to see if they come back on.

Also check the bulbs behind the cluster along with the rheostat's inner workings.

It could also be a contact in the head light switch

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77' 300D, "Cartman" SOLD @ 150K (didn't know what I had)
83' 300SD, "The Superdon" 325k+ @ 28mpg
95 E320 wagon, "Millennium Falcon" 231k+ @ 24 Mpg
95 E300D, "Sherley" 308k @ 33.69 Mpg, currently anticipating a head
99 Suzuki Intruder "Trudy" @ 45 mpg