DC nodal analysis with timed flashers and wire heating. Existing ideal leads are 0.01 Ω; new wires default to 18 AWG, 1 m copper. The battery has a 0.05 Ω internal resistance and a shared chassis. Battery negative is internally bonded to chassis. Bulbs and motors are fixed resistive equivalents; the sensor is a variable resistance. Relays pull in above 8 V. Fuses open immediately above their rating. This version does not model motor inrush, bulb temperature, PWM, ECU logic, or fuse time curves.

Bulb color intensity tracks calculated lamp power relative to its reference power. This is an illustrative glow, not measured visual brightness. Live current, voltage and power numbers are intentionally absent from component labels; use your test tools. Filament bulbs use warm light and LED examples use cool light. Two identical fixed-resistance bulbs in series each receive about half the voltage and a quarter of the power of one bulb alone. Real filament temperature and LED drivers can change this behavior.

Wire heat uses I²R, copper thermal mass, and an illustrative free-air cooling model at 20°C. The simulated 150°C insulation-failure threshold opens the wire; this is not a copper melting temperature or an ampacity rating. Packaging, insulation, bundling and airflow are not modeled. Flasher timing and minimum load are configurable training parameters. The injector's 8 A breaker trips instantly in this model, unlike a real tool's thermal time curve.

The voltmeter loads the circuit at 10 MΩ. The ammeter adds a 0.01 Ω path between probes and has a latching 10 A fuse. Open a wire and insert the probes in series for current. Resistance/continuity requires power off and measures all parallel paths with the battery disconnected. Unconnected terminals show OL. Multiple batteries share a common negative chassis.