I am having troble with my dash when I turn the headlights on my tach, amp gauge, oil presure gauge goes dead. I think it might be the ground but don't know what the color code is can anyone help me out on my 84 Z28?

All ground wires are black. Some may have a white stripe.

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'69 RS/SS396 pro street
427/4spd/9"

Main dash ground is black,and attached to steel frame of dash,just left of steering column.There is another ground on rear right cyl head.

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68 z28 ,68 rs 327 ,73 454 vette, 2 goofy kids

Does it only do it when the high beams are on? I just found my problem today... my lights / radio / ect were shutting off if my highs were on but not when the lows were on. It turned out to be the high beam indicator is free floating arround and grounding out.

i have the print for that if you need it. it is most likely the grounds at the dash support,(3 total i think) left of the steering column.