I replaced the Instrument Illumination Control Unit and everything is working as it should. This part is located behind the cluster, RH side.

Actual PN on the part I pulled is 003 545 63 32 and I replaced with an earlier version from an '89 with the PN referenced in my first post. the units look different but the pin numbers and plug are the same.

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1984 380 SL (Helga)