There's an lead with an LED (light emitting diode) that mounts with a small screw behind the speedometer. Not sure of it's purpose - speed monitoring for some reason. To my knowledge it is found only on 1987 & + models.:
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Also, on trucks equipped with premium trim levels, there is a FOC (fiber optic cable).
It steals a fraction of the available lumens from one of the backlighting lamps. There is a special adapter that twist locks into the socket (upper RH corner - looking fwd).
It transfers that light over to the ashtray - and casts a glow on the cigarette lighter.
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