Fuse Box Connections

Figure 1


Notes on Lucas 7FJ fuse box

Two fuses contained in the control box of series I cars are shown on circuit diagrams drawn between 1939 and 1947. Lucas RF 95 Regulators were used in late 1940's cars. The Morgan 4/4 series II had a separate fuse box containing 2 fuses from 1950 until the late 1960's. They are Lucas SF6 boxes which were used widely in many 1950's cars. Austin Healy, MGA, Triumph TR2, Austin A35 and Jaguar XK 150 are just a few to mention. These fuse boxes are still widely available on Ebay and companies like Holden (see link below). On Morgans the SF6 box was replaced in the late 1960's with a Lucas 7FJ containing four fuses with two spares.

The Lucas 7FJ fuse box on a 4/4 Morgan was located on the offside upper surface of the bulkhead until 1988. In 1989 a continental type fuse box with blade fuses replaced the 7FJ. It is mounted under the dashboard to this day. One of the four fuses on my 1972 Morgan looks like it is not connected to a supply. This is because fuses 3 and 4 are linked. Both are supplied by the red wire with green tracer (see figure 1) . All of the fuses are rated at 35 amps (17.5 amps continuous). Electrics connected to fuses 1, 3 and 4 do not require the ignition to be switched on. Fuse 2 does require the ignition to be switched on. Having removed the loom it is wise to use fine emery to clean the fuse holders. If the contacts are too corroded, a replacement fuse box and fuses can be obtained from the Holden Vintage & Classic company. There are variants of Lucas 7FJ boxes. If you require a new one, make sure you order the one with a link on the bottom (part-no. 37521 if ordering from Holden). Diagram 1 above should clarify the connections necessary to connect the loom and the ancillaries protected by the relative fuses. The starter solenoid shown above is the view from the bottom. It is important when rewiring to assure that the brown wire connected to fuse 1 is connected to the battery + terminal on the starter solenoid and not to the starter motor terminal.


When rewiring the Lucas 7FJ fuse box, look at the bottom and check that terminal 3 and 4 are the linked fuses.  DO NOT connect these terminals to the brown and white wires.

The brown wire with white trace, connected to the lighting switch is not NOT fused and is always at 12V potential. This wire must never be shorted to earth. The flasher switch and headlamp main beam wires are not fused and must be treated with care.If shorted to earth, these cables will burn out and may cause a fire.