Screenshot of dedicated wiring diagram confirming direct (LED) clock illumination from o/s sidelight circuit unique to 3.7 Roadster.

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The main chassis loom schematic shows instrument dimming rheostat connecting exclusively to BCU. It's clear this provides the logic to give full intensity illumination to Ford instruments during daylight, switching to rheostat control when it receives a trigger from side/headlight selection. In fact this is all sidelight selection does since actual sidelights (hence clock illumination) are permanently on with ignition.