My 8 had been re wired, but had the diodes in place, under the floor of the driver, but wires were broken and corroded.
First I redid the wires to the head lights(used original wires), then external powered the bulbs. You only need 2 wires (1 for hi N 1 for low) ---next remove the dimmer sw. 1 hot fused wire to the common post on the dimmer switch, 1 wire from the hi to a post 1 wire from the low to a post.
The hot must be 12V. for me to prevent tripping breakers , I ran the hi of a relay and a relay for the lo. That means installing 2 relays and getting fused power(12V) from
?? and my dimmer switch controls the relays not the bulbs.
My house is 12V. so it runs the coach lights.
No matter how the head lights are (12V or 24V) the grounds are super important, must be very solid.
The sockets 1 wire to ground N 1 to the hi the other to lo---- some all 4 on lo when on lo and only 2 on high when on high.