The wiring looms are entirely specific to the MGC, they cannot be interchanged with MGB looms despite the shared electrical fittings, switches, and many common components. The difference lies in the wire lengths, routing paths, and connector positions, all of which reflect the MGC's longer engine bay, different component locations (particularly the alternator, starter motor, oil filter, and cooling system layout), and the additional wiring required for the six-cylinder engine's distributor and spark plug positions. The main loom differs between AC and ACR alternator-equipped cars (the AC alternator uses an external regulator box requiring additional wiring, while the ACR has an internal regulator) and between home market and North American specifications (North American cars have additional wiring for emissions equipment, different lighting circuits, and the dual-circuit brake system warning light).
Loom Construction
Main looms are available in traditional cloth binding for period-correct restoration or vinyl binding for improved durability and moisture resistance. Cloth-bound looms are correct for concours presentation and have the authentic appearance expected by show judges, but the cloth binding absorbs moisture and can harbour corrosion at wire junctions. Vinyl-bound looms are more practical for cars in regular road use, as the vinyl sheds water and is easier to keep clean in the engine bay.
Body Looms and Extensions
Body looms differ between Roadster and GT, the GT has additional wiring for the rear hatch courtesy light and heated rear screen connection. Both cloth and vinyl binding are available. Extension looms for the dip switch, reverse light switch (manual gearbox), reverse and inhibitor switch (automatic gearbox), and overdrive circuit are available where the relevant equipment is fitted.
When replacing a wiring loom, all connections should be cleaned back to bright metal, and bullet connectors and spade terminals that have corroded should be replaced rather than reused, a poor connection in a new loom causes the same intermittent faults as the old loom it replaced.