The MGC was fitted with a negative earth 12-volt electrical system from the start of production, in common with the contemporary MGB Mark II, which adopted negative earth at the same time in 1967. This means the MGC avoids the positive-to-negative earth conversion complications that affect earlier MGAs and pre-1967 MGBs. Electrical components were originally all supplied by Lucas, though some items on later production were sourced from alternative manufacturers.
Alternator Charging
All MGCs were fitted with alternator charging from new, no MGC ever had a dynamo. Two alternator types were used during production. Cars up to the 1969 model year change point (engine numbers 29G/3200, 29GA/1400) were fitted with the 16AC type alternator, which uses a separate remote-mounted 4TR electronic control unit (regulator). From engine numbers 29G/3201 and 29GA/1401 onwards, the 16ACR alternator with a built-in regulator was fitted, dispensing with the external control box.
The visual difference is distinctive: the AC type has a black plastic moulding covering only half of the back of the unit, while the ACR type has a full-width cover enclosing the internal regulator.
Starter Motor
A Lucas M418G pre-engaged starter motor was fitted to all MGCs, the same type as the MGB of the equivalent period, typically painted in the same silver-green as the engine. The starter motor was modified from engine numbers 29G/624 and 29GA/127 with a new type of solenoid; the revised type was fitted to 29GB engines from the start of that series.
Wiring Looms
While wiring loom fittings and clips are shared with the MGB, the wiring looms themselves are entirely MGC-specific. Main looms are available in cloth or vinyl binding, and differ between AC alternator and ACR alternator-equipped cars, and between home market and North American specifications. Body looms differ between Roadster and GT models. Extension looms are available for the dip switch, reverse light switch (manual gearbox), reverse/inhibitor switch (automatic gearbox), and overdrive.
Battery
The MGC uses two 6-volt batteries connected in series to provide 12 volts, located in battery boxes beneath the floor behind the seats. Battery cables, earth, positive, and inter-battery, are all available, along with clamps, pads, bins, and battery security devices.
Fuse Protection
The electrical system is protected by a two-fuse fusebox with 35-amp and 50-amp fuses, the same type as the contemporary MGB Mark II.
Instruments
Speedometers and tachometers differ between UK/export and North American fascia types, and the speedometer is further complicated by three different rear axle ratios affecting calibration. Oil, water, and fuel gauges also differ between fascia types, with home market cars using a combined oil/water gauge and North American cars using separate electric gauges.