Alternator/negative ground conversion - XK 150

XK 150 alternator conversion by Fred Secker

The alternator I used is an 80 amp Delco Remy self-exciting unit - cost about $100.00

The lower alternator bracket uses the two original lower mounting points. These are horizontally aligned enabling the new bracket to be made from 1¼ x 3/16 flat bar bent at one end to form a lug with a second lug welded in place. Two points to bear in mind, (a) the alternator has a larger diameter than the generator so the lower mounting point  must be slightly lower than the original and (b) the front lug of the bracket will be very close to the steering column universal joint. The upper tensioning arm was sourced at a scrap yard. The original V-belt can be used. For the negative earth conversion the battery, ammeter and fuel pump capacitor connections must be swapped.

When fitting a self-regulating alternator the voltage regulator becomes redundant but the spade terminals on the regulator can be used to complete the necessary wiring without needing to cut or re-route any wires.

Remove the three coils from inside the regulator by simply undoing three nuts and snipping one soldered connection. Inside the empty body of the regulator use a short piece of wire to connect the F terminal to the D terminal.

There are three spade terminals labelled D, F and B. D has a pair of terminals, one large and one small. F has one small terminal and B has a pair of large terminals.

The wire from the alternator is the thick yellow one. Move this from the D terminal to the unused terminal of the B pair. This now connects the alternator to the battery. The thin yellow wire goes to the ignition warning light and should be placed on the small terminal of the D pair.

The yellow/green thin wire is the original field wire and should remain on the F terminal. At the alternator remove the rubber plug covering two small spade terminals. Connect the redundant yellow/green field wire to the spade terminal on the alternator that has 12 volts when alternator is running. This conveniently connects a signal from the alternator to the ignition warning light to enable it to indicate correctly.

Job done!