That's how the clock works in the older Benz. It isn't like a "standard" electric motor which is under a load constantly. Power is only used to "wind" the clock, the mechanical portion takes over, the spring winds down, the clock "re-winds" and the process continues.

This is a very simplified explanation of the actual process. If you wire the clock remotely and sit it on a bench you can hear the "click" as it resets.

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