On that same melted wiring harness you should find a pre-wired 6 pin connector (I think it's visible on the left wiring bundle) for Webasto/independent heater remote control receiver which has the supply from the same fuse F86 as the aerial amplifier. Wiring colour for that supply red/black. (Other connected wires on that connector brown/black and white/green, the rest 3 positions are empty.)

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E39 530dA -02 M-Sport Messing metallic
E53 X5 3.0dA -06 Sport Stratus grey
E70 X5 40d -12 M-Sport Space grey