Seems a ghost is hosting in the lighting cluster.

IN such a case: I do as follows

With a volt meter you check for voltage from where you reed 12 Volts
you follow the wire(s) that are suspicious
.
There has to be a point where there will no be continuity (instrum lights don' t shine)



succes
Kkurt
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240 '88 B200K wite sedan 255K km Europe virgo+all turbo gauges, Phoenix Gold + Kenwood ampli, Focal door speakers + tweeters, Kenwood 6'x 9', 10 CD changer in enlarged globe cabinet, dubble rear coil springs , hitch, fog lights, 2 extra rectangular pencil lights, 2 X 3 rear red driving lights