Brown lines on my 1980 and 1983.
Two brown lines go to key switch.
These two lines complete the circuit.

Make sure they are snug at the key (under dash) first.

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80 300D 340K Owned 30 yrs
83 300SD 440K Owned 9 yrs - Daily Driver 150mi/day
02 Z71 Suburban 117,000
15 Toyota Prius 2600 miles
00 Harley Sportster 24k
09 Yamaha R6
03 Ninja 250