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From the very beginning, Mark's vehicle had lower voltage in the battery system. It was always 1.5 volts less than that of the battery. With the engine running, the cigarette lighter, central locking, and window regulators received only 11.9 volts. If the car was not started but ignition turned on, it dropped to just 10.5 volts.

Thought about finding a bad connection where the voltage drop occurred by 1.5 volts. But upon testing it appeared that there were no such connections, and the voltage drop was evenly distributed over a long wire from the battery to the ignition switch, then back under the hood to the coil, totaling around 5 meters of cable!

The ignition coil consumes a lot of current and causes a drop in voltage in the vehicle's electrical system. The voltage reaching the ignition coil is less than 10 volts.

Plus from the battery (point 0) goes to the lock at point 1, then to the coil (point 2). Five meters of extra wire! Voltage drop up to 2 volts!

It seems that such a solution with a long wire was applied by the manufacturer to complicate car theft. However, now reliable electrical operation is more important for me. Therefore, I made this reverse wire from the ignition switch (indicated on the diagram by a red arrow) controlling, and near the ignition coil and battery installed an additional relay that feeds power to the coil.

The relay should be placed under the hood somewhere between the battery and the ignition coil. Then losses in wires will be minimal.

As a result of this modification, voltage at the ignition coil increased by 3 volts which should improve engine starting and operation. The vehicle's electrical system voltage increased by 1.5 volts. As a consequence, window lifters speeded up. Central locking became more precise.

All current consumers work from the plus IGN - rear windshield heating and others, so installing such an additional relay will significantly reduce load on wires in the wiring harness under the dashboard and not only keep electricals in order but also reduce the probability of wire melting and ignition in retro cars.