The MGF and MG TF use two distinct fuseboxes: one in the engine compartment covering high-current circuits (starter, alternator, EPAS, headlamps, cooling fans), and one in the passenger compartment covering lower-current cabin circuits (interior lights, instruments, radio, airbag supply). Both fuseboxes are catalogued as separate assemblies with their own production changes, and both are accessed at different points in the car, engine bay fusebox under a lid at the front of the engine compartment, passenger fusebox behind a trim panel on the passenger-side A-post area.
Engine Compartment Fusebox, Three Variants
The engine compartment fusebox changed specification twice across production. MGF cars up to VIN XD511058 used one assembly with its own upper cover. MGF cars from XD511059 (the Mk1/Mk2 transition) used a revised assembly with a different cover. MG TF cars from 2002 onwards used a third assembly with its own cover again. The three assemblies are not interchangeable and the cover must be matched to the box.
Mounting is via two M8 bolts to the bulkhead bracket.
Passenger Compartment Fusebox, Two Variants and Handed Mounting
The passenger compartment fusebox changed once during production, at MG TF VIN 3D610318. MGF and MG TF cars up to that VIN used one assembly; MG TF cars from 3D610318 used a revised assembly. The mounting bracket is additionally handed by steering position, with separate RHD and LHD brackets for MGF and MG TF up to 4D620548, then a single universal bracket for MG TF from 4D620549. Ordering the correct fusebox requires knowing the VIN; ordering the mounting bracket requires both VIN and steering hand.
Blade Fuses and High-Amperage Fuseblocks
Standard blade fuses are colour-coded by rating: 10A red, 15A blue, 20A yellow, and 30A green, available singly or in packs of five. A 5A fuse specific to the airbag control circuit is catalogued as a dedicated part for MGF and MG TF up to 4D620548 (post-4D620549 TF cars use a standard blade fuse for the same function). Never fit a fuse of higher rating than the circuit specifies, the fuse protects the wiring from overheating in the event of a short circuit, and a higher-rated fuse can allow enough current to melt wiring insulation and cause fire. For the high-current EPAS, alternator, and starter circuits, larger fuseblocks are catalogued in 30A, 40A, and 60A ratings, these use a different connector style from the blade fuses and are specific to the engine bay fusebox.
EPAS and Alternator Fuse, Production Change at YD522573
The MGF's main power-steering fuse changed with the alternator design upgrade at VIN YD522573 (the same breakpoint as the A115i ? GCB2 alternator transition covered on the Alternator page). Early EPAS cars use a 40A fuse dedicated to the steering circuit; from YD522573 onwards a combined 80A alternator-circuit fuse was fitted, covering both the charging output and the EPAS feed. A blown fuse of either rating disables the electric power steering, expected given the 25-miles-on-failed-alternator drain scenario covered in the Electrics parent framing.
Engine Management Relays, Quantity Changed
The engine management relay is the most commonly replaced relay on the MGF/TF, responsible for supplying power to the MEMS ECU, fuel pump, coil packs, and injectors under ECU command. MGF cars and MG TF cars up to VIN 3D610317 use one engine management relay. From MG TF VIN 3D610318 onwards, the revised engine management architecture uses three relays of the same specification, replacements are often done as a set to ensure consistent service life. A failing engine management relay causes intermittent starting, random misfires, or complete engine cut-out under load.
The fuel pump relay shares the same part number as the later engine management relay.
Other Relays and Control Units
Air conditioning relays changed specification at VIN 4D620548, two variants are catalogued. A yellow multipurpose relay covers front fog lamps (MG TF) and the hard top heated rear window on both models. A specific black relay was introduced on MG TF from 5D639631 for the soft top heated rear window. An electronic indicator flasher unit replaces the original thermal unit, necessary for conversions to LED indicators which don't draw enough current to trigger thermal flashers.
The multi-function ECU controls body electrical functions including courtesy lamp timing, intermittent wipers, and lock actuation on MGF and MG TF cars up to 4D620548. A dedicated one-touch window lift control unit handles the single-pulse window-down-full operation. EPAS ECU variants and their specific production changes are catalogued alongside the other EPAS components