The original was a mechanical device that had a wire wound around a bi-metal strip attached to a set of contact points. As the current flowed through the wire coil it heated up and caused the bi-metal contacts to open this turned the current off and they closed causing the current to flow again. This cycled reasonably quickly causing a steady voltage across the contacts.
As with all things mechanical and electrical contacts, they fatigue/burn/fail in time. The electronic version has no moving parts, produces a stable, constant 10 volts, which is required for the gauges to operate, and will last the life of the vehical - baring massive power surges, lightning strikes and hooking it up the wrong way round
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David L
My greatest fear in life is that when I die my wife will sell my Mini and tools for the price I told her I paid for them!